[jsk_topic_tools/SynchronizedThrottle] Reset sync policy in destructor

[iory]

In SynchronizedThrottle, if node is killed, the following error occurs.

terminate called after throwing an instance of 'boost::exception_detail::clone_impl<boost::exception_detail::error_info_injector<boost::lock_error> >'
  what():  boost: mutex lock failed in pthread_mutex_lock: Invalid argument
Aborted

This PR fixes this behavior.
Also see ros/ros_comm#720 .

[YutoUchimi]

without this PR
https://travis-ci.org/jsk-ros-pkg/jsk_common/jobs/600547156

5449[jsk_topic_tools:make] -- run_tests.py: execute commands
5450[jsk_topic_tools:make]   /opt/ros/indigo/share/rostest/cmake/../../../bin/rostest --pkgdir=/home/travis/ros/ws_jsk_common/src/jsk_common/jsk_topic_tools --package=jsk_topic_tools --results-filename test_test_synchronized_throttle.xml --results-base-dir /home/travis/ros/ws_jsk_common/build/jsk_topic_tools/test_results /home/travis/ros/ws_jsk_common/src/jsk_common/jsk_topic_tools/test/test_synchronized_throttle.test 
5451[jsk_topic_tools:make] ... logging to /home/travis/.ros/log/rostest-c0f29cbedc7b-30222.log
5452[jsk_topic_tools:make] [ROSUNIT] Outputting test results to /home/travis/ros/ws_jsk_common/build/jsk_topic_tools/test_results/jsk_topic_tools/rostest-test_test_synchronized_throttle.xml
5453[jsk_topic_tools:make] [ INFO] [1571637630.327067104]: Initializing nodelet with 2 worker threads.
5454[jsk_topic_tools:make] [ INFO] [1571637630.391821098]: Initializing nodelet with 2 worker threads.
5455[jsk_topic_tools:make] [ INFO] [1571637635.449322452]: All topics are now published and synchronized
5456[jsk_topic_tools:make] terminate called after throwing an instance of 'boost::exception_detail::clone_impl<boost::exception_detail::error_info_injector<boost::lock_error> >'
5457[jsk_topic_tools:make]   what():  boost: mutex lock failed in pthread_mutex_lock: Invalid argument
5458All topics are now published and synchronized
5459[jsk_topic_tools:make] testtest_synchronized_throttle ... ok
5460[jsk_topic_tools:make] 
5461[jsk_topic_tools:make] [ROSTEST]-----------------------------------------------------------------------
5462[jsk_topic_tools:make] 
5463[jsk_topic_tools:make] [jsk_topic_tools.rosunit-test_synchronized_throttle/test_async][passed]
5464[jsk_topic_tools:make] [jsk_topic_tools.rosunit-test_synchronized_throttle/test_async_delay][passed]
5465[jsk_topic_tools:make] [jsk_topic_tools.rosunit-test_synchronized_throttle/test_sync][passed]
5466[jsk_topic_tools:make] [jsk_topic_tools.rosunit-test_synchronized_throttle/test_sync_delay][passed]
5467[jsk_topic_tools:make] 
5468[jsk_topic_tools:make] SUMMARY
5469[jsk_topic_tools:make]  * RESULT: SUCCESS
5470[jsk_topic_tools:make]  * TESTS: 4
5471[jsk_topic_tools:make]  * ERRORS: 0
5472[jsk_topic_tools:make]  * FAILURES: 0
5473[jsk_topic_tools:make] 
5474[jsk_topic_tools:make] rostest log file is in /home/travis/.ros/log/rostest-c0f29cbedc7b-30222.log
5475[jsk_topic_tools:make] -- run_tests.py: verify result "/home/travis/ros/ws_jsk_common/build/jsk_topic_tools/test_results/jsk_topic_tools/rostest-test_test_synchronized_throttle.xml"

with this PR
https://travis-ci.org/jsk-ros-pkg/jsk_common/jobs/609161766

5059[jsk_topic_tools:make] -- run_tests.py: execute commands
5060[jsk_topic_tools:make]   /opt/ros/indigo/share/rostest/cmake/../../../bin/rostest --pkgdir=/home/travis/ros/ws_jsk_common/src/jsk_common/jsk_topic_tools --package=jsk_topic_tools --results-filename test_test_synchronized_throttle.xml --results-base-dir /home/travis/ros/ws_jsk_common/build/jsk_topic_tools/test_results /home/travis/ros/ws_jsk_common/src/jsk_common/jsk_topic_tools/test/test_synchronized_throttle.test 
5061[jsk_topic_tools:make] ... logging to /home/travis/.ros/log/rostest-fb3e36f3268c-25814.log
5062[jsk_topic_tools:make] [ROSUNIT] Outputting test results to /home/travis/ros/ws_jsk_common/build/jsk_topic_tools/test_results/jsk_topic_tools/rostest-test_test_synchronized_throttle.xml
5063[jsk_topic_tools:make] [ INFO] [1573212123.121521430]: Initializing nodelet with 2 worker threads.
5064[jsk_topic_tools:make] [ INFO] [1573212123.209628651]: Initializing nodelet with 2 worker threads.
5065[jsk_topic_tools:make] [ INFO] [1573212128.273663134]: All topics are now published and synchronized
5066[jsk_topic_tools:make] [ INFO] [1573212128.291686189]: All topics are now published and synchronized
5067[jsk_topic_tools:make] testtest_synchronized_throttle ... ok
5068[jsk_topic_tools:make] 
5069[jsk_topic_tools:make] [ROSTEST]-----------------------------------------------------------------------
5070[jsk_topic_tools:make] 
5071[jsk_topic_tools:make] [jsk_topic_tools.rosunit-test_synchronized_throttle/test_async][passed]
5072[jsk_topic_tools:make] [jsk_topic_tools.rosunit-test_synchronized_throttle/test_async_delay][passed]
5073[jsk_topic_tools:make] [jsk_topic_tools.rosunit-test_synchronized_throttle/test_sync][passed]
5074[jsk_topic_tools:make] [jsk_topic_tools.rosunit-test_synchronized_throttle/test_sync_delay][passed]
5075[jsk_topic_tools:make] 
5076[jsk_topic_tools:make] SUMMARY
5077[jsk_topic_tools:make]  * RESULT: SUCCESS
5078[jsk_topic_tools:make]  * TESTS: 4
5079[jsk_topic_tools:make]  * ERRORS: 0
5080[jsk_topic_tools:make]  * FAILURES: 0
5081[jsk_topic_tools:make] 
5082[jsk_topic_tools:make] rostest log file is in /home/travis/.ros/log/rostest-fb3e36f3268c-25814.log
5083[jsk_topic_tools:make] -- run_tests.py: verify result "/home/travis/ros/ws_jsk_common/build/jsk_topic_tools/test_results/jsk_topic_tools/rostest-test_test_synchronized_throttle.xml"