Fix filesink drop messages improved

[KjellKod]

PULL REQUEST DESCRIPTION

Incorporates #478

Commit 6c6122f introduced a bug where 99 out of 100 logs were actually dumped. Bug discovered while using two sinks : FileSink and the stdout example sink. I had every messages in stdout sink, but very few in the log file.

Bug Description

The bug would happen when enough messages were put into a buffer for it to flush.
The unit tests were not setup to trigger buffer flushing.

Fix description

• @ryanammoury fixed the issue in Fix FileSink dropping messages  #478
• @KjellKod updated unit tests to first trigger this issue and then resolving it with ^ pull request.

Testing

• [ x] This new/modified code was covered by unit tests.

• [x ] (insight) Was all tests written using TDD (Test Driven Development) style?

• [ x] The CI (Windows, Linux, OSX) are working without issues.

• [ x] The testing steps 1 - 2 below were followed

step 1

mkdir build; cd build; cmake -DADD_G3LOG_UNIT_TEST=ON ..

// linux/osx alternative, simply run: ./scripts/buildAndRunTests.sh

step 2: use one of these alternatives to run tests:

• Cross-Platform: ctest
• or ctest -V for verbose output
• Linux: make test