Fix promise timeout test for mac os

[pnoltes]

The promise timeout test on macos github CI are failing from time to time. I cannot reproduce this on my mac (10.15.7)

2021-03-25T12:23:17.5997380Z 12: /Users/runner/work/celix/celix/libs/promises/gtest/src/VoidPromisesTestSuite.cc:205: Failure
2021-03-25T12:23:17.5998290Z 12: Expected equality of these values:
2021-03-25T12:23:17.5998710Z 12:   false
2021-03-25T12:23:17.5999110Z 12:   secondSuccessCalled
2021-03-25T12:23:17.5999500Z 12:     Which is: 1
2021-03-25T12:23:17.6000230Z 12: /Users/runner/work/celix/celix/libs/promises/gtest/src/VoidPromisesTestSuite.cc:206: Failure
2021-03-25T12:23:17.6000980Z 12: Expected equality of these values:
2021-03-25T12:23:17.6001380Z 12:   true
2021-03-25T12:23:17.6001740Z 12:   secondFailedCalled
2021-03-25T12:23:17.6002120Z 12:     Which is: 0