Fix console launcher `--uid` option

[sormuras]

The discussion in #4583 combined with the linked issue eclipse-jdt/eclipse.jdt.core#4053 shows that two bugs are hiding here. One is in JUnit:

When...

      --uid, --select-unique-id=UNIQUE-ID...
                             Select a unique id for test discovery. This option can be
                               repeated.

...is used as the sole selector, the console launcher shows a false error message reading:

Please specify an explicit selector option or use `--scan-class-path` or `--scan-modules`

There exists a work-around, though. Use --select uid:UNIQUE-ID... to prevent the error to happen.

According to what I read from eclipse-jdt/eclipse.jdt.core#4053, the other bug seems to be in ecj and therefore cannot be addressed here.

[trancexpress]

Thank you for looking into this!