Capture one more timestamp for an application when ApplicationClientProtocol#getNewApplication is executed

The application submission time ( when submitApplication is called) is collected by RM and application history server. But it doesn't capture when the client calls newApplication method. The delta between newApplication and submitApplication could be useful if the client submits large jar files. This metric will be useful for https://issues.apache.org/jira/browse/YARN-1492.