tests: Remove check/test/tests subdir targets

tests: Remove check/test/tests subdir targets

Since commit a62de618 (Build util tests properly with make check),
running 'make check' in tests/ also runs 'make check' in each of the
tests subdirectories, which builds the tests in that dir. (And the
same goes for 'make test' and 'make tests'.)

This does ensure that the tests are built before we run them, but it's
a bit strange to build the tests under 'make check', a target that
usually runs tests.

We do this in the top-level tests dir to make sure that the tests are
built, but this purpose is served by the existing 'make all' target.
So to reduce some duplication of logic, and reduce the number of
targets the subdirs need to implement, just have 'make check' depend
on 'make all', so we know the tests are built when we go to run them.

Change-Id: I2fcbe88daeeae94cd7ef7a4a8326c4b56fadee5a
Reviewed-on: https://gerrit.openafs.org/14636
Reviewed-by: Michael Meffie <mmeffie@sinenomine.net>
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>