Jetty init may fail if directory name contains "master"

InfoServer.getWebAppsPath() unsafely assumes that any instance of the string "master" in the full path to hbase-webapps can be truncated. This breaks in the case where hbase is installed in a directory such as "/my/hbasemaster/".

The result is that Jetty initialization will fail since the master determines an incorrect path to hbase-webapps. The master still runs but the web UI returns 503.

I have a patch for this problem that I'll upload soon.