[script] Added --unlock_unsafe_flags to start_kudu.sh

Without --unlock_unsafe_flags start_kudu.sh shows
warning:
WARNING: Logging before InitGoogleLogging() is written to STDERR
WARNING: Logging before InitGoogleLogging() is written to STDERR
E0421 21:54:53.600564 17547 hybrid_clock.cc:157] --unlock_unsafe_flags
should be set if configuring --time_source to be system_unsync or mock
E0421 21:54:53.600500 17545 hybrid_clock.cc:157] --unlock_unsafe_flags
should be set if configuring --time_source to be system_unsync or mock

Change-Id: If7cc93849cf61d5a80001f4fd544dd678426fa5d
Reviewed-on: http://gerrit.cloudera.org:8080/15780
Tested-by: Kudu Jenkins
Reviewed-by: Alexey Serbin <aserbin@cloudera.com>
1 file changed