Allow rename of a host group

RN: host groups can now be renamed with IPA CLI:
RN: 'ipa hostgroup-mod group-name --rename new-name'.
RN: Protected hostgroups ('ipaservers') cannot be renamed.

Fixes: https://pagure.io/freeipa/issue/6783
Signed-off-by: Alexander Bokovoy <abokovoy@redhat.com>
Reviewed-By: Florence Blanc-Renaud <frenaud@redhat.com>
Reviewed-By: Rob Crittenden <rcritten@redhat.com>

API.txt

@@ -2789,7 +2789,7 @@ output: ListOfEntries('result')
 output: Output('summary', type=[<type 'unicode'>, <type 'NoneType'>])
 output: Output('truncated', type=[<type 'bool'>])
 command: hostgroup_mod/1
-args: 1,9,3
+args: 1,10,3
 arg: Str('cn', cli_name='hostgroup_name')
 option: Str('addattr*', cli_name='addattr')
 option: Flag('all', autofill=True, cli_name='all', default=False)
@@ -2797,6 +2797,7 @@ option: Str('delattr*', cli_name='delattr')
 option: Str('description?', autofill=False, cli_name='desc')
 option: Flag('no_members', autofill=True, default=False)
 option: Flag('raw', autofill=True, cli_name='raw', default=False)
+option: Str('rename?', cli_name='rename')
 option: Flag('rights', autofill=True, default=False)
 option: Str('setattr*', cli_name='setattr')
 option: Str('version?')