Improve POSIX mutex test

[shankar-in]

Brief feature description

Using the While loop will consume CPU cycles and other threads will have to wait. Using the sleep_for will free up the CPU for the define time so that other threads can utilize.-

Detailed information

The test_posix_mutex.cpp has DestructorFailsOnLockedMutex test case. It uses deadline timer with a While loop and this can be improved by replacing with sleep_for. Hint suggestion from @elBoberido ,
EXPECT_DEATH({{ iox::posix::mutex mtx{false}; mtx.lock; }}, ".*");