Dev: tomcat: avoid unnecessary su when root

This commit should be fold into this before merging to the upstream:
https://github.com/kskmori/resource-agents/commit/3f170b0b4c8c78e85fd7ad950c8f259bdbd580a8

Although the original code just works with no problem,
we're going to fix it not to record unnecessary audit.log.
Thanks to knakahira for testing.