malcontent-client: Implement --quiet for check subcommand

When run with `--quiet`, the `check` subcommand will now print nothing.
It continues to exit with an appropriate exit status.

Signed-off-by: Philip Withnall <withnall@endlessm.com>

malcontent-client/malcontent-client.py

@@ -216,10 +216,12 @@ def command_check(user, path, quiet=False, interactive=True):
         noun = 'Path'
 
     if is_allowed:
+        if not quiet:
             print('{} {} is allowed by app filter for user {}'.format(
                 noun, path, user_id))
         return
     else:
+        if not quiet:
             print('{} {} is not allowed by app filter for user {}'.format(
                 noun, path, user_id))
         raise SystemExit(EXIT_PATH_NOT_ALLOWED)