Makefile/travis: run offline tests in CI

Internet is sometimes flaky in CI. Therefore, in order to avoid unit
tests from failing intermittently, don't run the cURL tests which
download files from s3.

Makefile

@@ -136,6 +136,9 @@ run_all_tests: default
 run_unit_tests: default
 	build/default/unit_tests_runner
 
+run_unit_tests_offline: default
+	build/default/unit_tests_runner --gtest_filter="-CurlTest.*"
+
 run_integration_tests: default
 	build/default/integration_tests/integration_tests_runner
 

travis-docker-build.sh

@@ -2,7 +2,7 @@
 
 set -e
 
-make BUILD_TYPE=Debug run_unit_tests -j4
+make BUILD_TYPE=Debug run_unit_tests_offline -j4
 make default install
 make fix_style
 (cd example/takeoff_land && mkdir build && cd build && cmake -DCMAKE_BUILD_TYPE=Debug .. && make)
@@ -11,7 +11,7 @@ make fix_style
 make clean
 git clean -dfx
 
-make BUILD_TYPE=Release run_unit_tests -j4
+make BUILD_TYPE=Release run_unit_tests_offline -j4
 make default install
 make fix_style
 (cd example/takeoff_land && mkdir build && cd build && cmake -DCMAKE_BUILD_TYPE=Release .. && make)