Fix exit value of vme4l_mtest

Created by: HarryWaschkeit

Wanted to use vme4l_mtest in environmental tests of A025 (against A021C) and found out that the exit value is wrong under certain circumstances. I found out that a macro is used for general function abortion (CHK()) which doesn't touch the global error counter "tot_errors". The latter, however, is used for exit value, so if the only error in program is triggered by that macro, for the calling process it seems that everything went ok - bummer! Also I didn't understand why 'tot_errors' isn't used at all for return value in main() ...