permission plugin: Make --target available in the CLI

This was left out by mistake when permissions were refactored.
The API is already tested.

https://fedorahosted.org/freeipa/ticket/4522

ipalib/plugins/permission.py

@@ -297,7 +297,6 @@ class permission(baseldap.LDAPObject):
             'ipapermtarget?',
             cli_name='target',
             label=_('ACI target DN'),
-            flags={'no_option'}
         ),
 
         Str('memberof*',