Add ocis idm resetpassword subcommand

This allows resetting the ocis admin user's password (when ocis is
not running) when running with the builtin LDAP server.

Fixes #4084

services/idm/pkg/command/root.go

@@ -18,6 +18,7 @@ func GetCommands(cfg *config.Config) cli.Commands {
 		Server(cfg),
 
 		// interaction with this service
+		ResetPassword(cfg),
 
 		// infos about this service
 		Health(cfg),