run-tests: make sure not to include the bad APKs in tests/

These APKs are meant for specific tests, not the tests that want just a
collection of good APKs.
run-tests: properly handle zero and multiple args

The test for the help flag threw an error if there were 0 args, or if arg 1
was set to a space-separated list.  The -z tests would fail if the arg was
set to a space-separated list.
Merge branch 'master' into 'master'

fix bugs in run-tests scripts

This fixes a couple of subtle bugs in `./run-tests` that only showed up recently.

See merge request !30