selftest: Disable full audit logging in selftest

selftest: Disable full audit logging in selftest

Commit 6eba42f activated the full_audit and time_audit modules for the
simpleserver config to trigger the check that all VFS functions are
implemented in these two modules. This resulted in all operations being
logged to syslog during a test run.

Change the full_audit configuration to keep loading the modules, but not
log anything from full_audit to not slow down the test or spam the logs.

Signed-off-by: Christof Schmitt <cs@samba.org>
Reviewed-by: Jeremy Allison <jra@samba.org>