tests.py: add ability to run only tests which match a regex

This way it will be possible to start all java tests like this:

  $ scripts/test.py --name java.*
    TEST java                                OK  (1.556 s)
    TEST java-perms                          OK  (1.323 s)
  OK (2 tests run, 2.880 s)

Signed-off-by: Tomasz Grabiec <tgrabiec@cloudius-systems.com>
Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>