tests: fix dependencies.

* tests/local.mk (check_SCRIPTS): Add atlocal and atconfig so
that they are properly updated before running tests.
(RUN_TESTSUITE_deps): New.
Use it to factor the dependencies of "*-check" targets,
especially those that don't bounce to the regular
"check-local" target, since then they don't benefit from the
proper dependencies (such as atlocal).