Beautify tests

Make acceptance tests faster by enabling parallel tests harness, plus some minor fixes like automatically setting proper permissions for test files. See details in commit log.

What is still ugly is that I'm using the "testall" script to run each individual test (TODO create a "runtest" from scratch) and that logging is overwriting the previous tests. Finally a couple of tests in 16_cf-serverd/ fail because another serverd instance is bound to the port. I thought acceptance tests were unrelated to serverd, do we really need such tests here?

Our acceptance testsuite is still unacceptably slow, probably due to multiple forks and file creation on every test for checking success, but this is a start. Since the testsuite is heavily I/O bound, "make -j NCPU+1 check" seems optimal for now.