Separate 'awaitTestStartCommand()' log tests

'awaitTestStartCommand()' log tests are now a separate unit test suite
because I'm going to have to manually mock 'writeLog()' in order to
test its 'va_list' ability (it takes printf formatting)
Refactor: Break out common functions

Break out 'readFromMaster()' call-back functions that are common for
"test_control_tests.c" and "test_control_logging_tests.c"