Unit Test Failures in Asynchronous Task Executor on Ubuntu

[djeong20]

At present, the unit test for the asynchronous task executor experiences occasional failures during pdebuild on Ubuntu, which highlights the need for a thorough review and enhancement of our testing process.

40/40 unittest_nntrainer_task          TIMEOUT        120.13s   killed by signal 15 SIGTERM
>>> MALLOC_PERTURB_=227 /build/nntrainer-0.5.0/build/test/unittest/unittest_nntrainer_task --gtest_output=xml:/build/nntrainer-0.5.0/build/unittest_nntrainer_task.xml
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[==========] Running 6 tests from 1 test suite.
[----------] Global test environment set-up.
[----------] 6 tests from TaskExecutorTest
[ RUN      ] TaskExecutorTest.create_01_p
[       OK ] TaskExecutorTest.create_01_p (0 ms)
[ RUN      ] TaskExecutorTest.task_create_01_p
[       OK ] TaskExecutorTest.task_create_01_p (6 ms)
[ RUN      ] TaskExecutorTest.task_async_create_01_p
[       OK ] TaskExecutorTest.task_async_create_01_p (0 ms)
[ RUN      ] TaskExecutorTest.run_01_p
[       OK ] TaskExecutorTest.run_01_p (6 ms)
[ RUN      ] TaskExecutorTest.run_async_01_p
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Summary of Failures:

40/40 unittest_nntrainer_task          TIMEOUT        120.13s   killed by signal 15 SIGTERM

[skykongkong8]

I could find the similar error occasionally outbreaks at Tizen x86_64 gbs build as well.