'awaitTestStartCommand()' log test start command

'awaitTestStartCommand()' log reception of test start command
Refactor: 'unexpectedDataReceived' set by call-backs

The information about whether or not the "read_from_master_callbacks"
are returning an unexpected message instead of the expected test start
command is now the responsibility of these call-backs
Rename: 'unexpectedDataReceived()'

'unexpectedDataReceived()' -> 'unexpectedMessageReceivedFromMaster()'