test_pthread_cond_signal_1_1 is flaky

`test_pthread_cond_signal_1_1` has very small timeout during which main thread wakes side threads
and expect them to update flag. This causes that when tests are run on node.js this particular test fails
not because tested function (`pthread_cond_signal`) actually fails but due to the fact that woken up
side threads haven't get CPU time and haven't managed to update flag on time.

Observed behavior:
- When this test is run alone it never fails
- When whole test suite is run sequentially this test fails once per 100 runs
- When whole test suite is run in parallel this tests fails once per 10 runs