Clean up files generated by make check.
Clean up files generated by make check.

* tests/clean-socketdir: Remove more test-generated files.
--

Running make check may generate more files in the test directory
(notably, if the tests are run while a token is present, the agent
will have written down the shadow keys), that we need to cleanup
afterwards.

Signed-off-by: Damien Goutte-Gattat <3a260918a4ae0abc8ac3e544c6df1814a2596a5f@incenp.org>

gpg/scute,gpg/scute,gpg/scute