SENTRY-432: Made following changes :
            - Fix Sentry HDFS Integration test to start HMS after HDFS exits safemode
            - Ensure privileges granted/revoked on Db propogates to table directories
            - Cleaned up more log messages
            - Serialize updates from Sentry to Metastore to reduce number of sync messages
            - Add flag to switch to TBinaryProtocol on SentryHDFSServiceClient
            - Remove Unknown protocol warning from Sentry Service
            - Added more test cases
            - Add /lib/plugins folder to sentry classpath