fix for 'un-set' token realm in web gui and delete Tokenrealm

the un-set was not able after a first selection of tokenrealm
as a gloal Array was not reset on the right place
in addition the gui provided multiple (same) realms to the server
which could have caused the problem

closes #12620

Change-Id: If6d08fb10a6859ffbbf5b36c3fb25e78bdf7cc59