parser: fix cache reference leak

Drop the reference to the libapparmor policy_cache pseudo object when
the parser is done.

Signed-off-by: Steve Beattie <steve@nxnw.org>
Acked-by: Seth Arnold <seth.arnold@canonical.com>

parser/parser_main.c

@@ -992,6 +992,7 @@ int main(int argc, char *argv[])
 
 	if (ofile)
 		fclose(ofile);
+	aa_policy_cache_unref(policy_cache);
 
 	return last_error;
 }