CDAP-471 - Validate Service Handlers during deploy time.

1) In standalone, now stops all components, if one fails. JIRA issue has been opened to restart runnables if they fail: https://issues.cask.co/browse/CDAP-471
2) Validate the handlers that user passes in during deploy time
3) Move construction of NettyHttpServer to constructor of ServiceHttpServer (from startup)
4) Add a small test case to test (2)

https://bamboo-prod.continuuity.com/browse/CDAP-DUT79
Don't need to take in a ``pathPrefix`` here since you always call it with an empty string.