Bug in xmlns for grantowner and grantadmin / not in sync with JEP-0045
In order to keep the openfire compability, this fix needs to be delayed until Openfire 3.7.2 has been official released.
Since the shortly released openfire 4.8.0 is aware of the current XEP-45 spec, the fix for this issue can be commited.
MUC.getAdmins() is also using the wrong namespace. As reported in
Re-opening because of https://community.igniterealtime.org/thread/53348
Smack's MultiUserChat.grantAdmin() and .revokeAdmin should also use the admin namespace and not the owner namespace.