couchbase-cli help for index mode slightly incorrect

Build 1914

The help for couchbase-cli cluster-init shows:
...
--index-storage-setting index storage type [default, memopt]
--services=data,index,query services that server runs
...

However, --index-storage-setting=default is not valid (should be [forestdb, memopt] )

Also, the help should show --index-storage-setting=[forestdb,memopt] to show the user that they need to have an '=' in there instead of just the flag alone.