parser: add empty config file for parser caching tests

The caching tests will fail if a warning is thrown. Some setups may
not have a parser config file in the default location which results
in the warning
  config file '/etc/apparmor/parser.conf' not found

which causes the tests to fail.

PR: https://gitlab.com/apparmor/apparmor/merge_requests/175
Acked-by: Seth Arnold <seth.arnold@canonical.com>
Signed-off-by: John Johansen <john.johansen@canonical.com>

parser/tst/caching.py

@@ -68,7 +68,9 @@ class AAParserCachingCommon(testlib.AATestTemplate):
             self.do_cleanup = False
             self.debug = True
 
-        self.cmd_prefix = [config.parser, '--base', self.tmp_dir, '--skip-kernel-load']
+        # Warnings break the test harness, but chroots may not be setup
+        # to have the config file, etc.
+        self.cmd_prefix = [config.parser, '--config-file=./parser.conf', '--base', self.tmp_dir, '--skip-kernel-load']
 
         if not self.is_apparmorfs_mounted():
             self.cmd_prefix += ['-M', './features_files/features.all']