user-manage should allow a switch for simple update

Following are options for user-manage:
User manage options:
--delete Delete an existing RBAC user
--list List all RBAC users and their roles
--my-roles List my roles
--set Create a new RBAC user
--rbac-username <username> The RBAC username
--rbac-password <password> The RBAC password
--rbac-name <name> The full name of the user
--roles <roles_list> The roles for the specified user
--auth-domain <domain> The authentication type for the specified user

Execute the command below:

root@node1-cb450-ubuntu14:/opt/couchbase/bin# ./couchbase-cli user-manage --role admin --rbac-username ritam --auth-domain=local -c localhost -u Administrator -p password

ERROR: Must specify --delete, --list, --my_roles or --set

--set indicates that it is for user creation and both username and password need to be passed command to be run.
A switch to update or allow set to run with username and roles.