Remove group editing for readonly groups

Bug: 5209461 Uneditable groups (i.e. Circles from G+)
     seems to be editable, even if they aren't

Added a check that removes the edit button in the Group Details
fragment is the group is read-only.

Change-Id: I83b403c6b4b69d86b52827810741e86ace2e8c53
1 file changed