Use 'cvs version' instead of 'cvs rls' to test remote repositories.
Review Request #5831 — Created May 15, 2014 and submitted
'cvs rls' is only available in CVS 1.12+, which isn't yet considered stable.
Fortunately, if 'cvs version' is run with a CVSROOT, it will end up checking
whether that CVSROOT is valid, which is perfect for our needs.
Ran unit tests.