fix: exit with clear error when --waitFor value is not a valid number

[mugiwaraluffy56]

passing an invalid number to --waitFor (e.g. --waitFor abcsec) would silently set the timeout to 0ms. the suffix check passed because the unit was correct, but strconv.ParseInt returned 0 on the unparseable prefix and the error was discarded with _. the test then fired with a zero timeout and always failed, with no indication of what went wrong.

this also affects the invalid-suffix path: the old code printed a warning but did not exit, so the command continued with whatever value waitForMilliseconds happened to have.

both cases now exit with a clear message pointing at the bad value.

tested manually:

$ microcks test ... --waitFor abcsec
--waitFor value "abcsec" is not a valid number

$ microcks test ... --waitFor 30s
--waitFor format is wrong. Accepted units are: milli, sec, min (e.g. 500milli, 30sec, 5min)

[lbroudoux]

Looks legit. Thank you very much.