Issue #2710427 by smustgrave, longwave, akhoury, alexpott, ChaseOnTheWeb,...

Issue #2710427 by smustgrave, longwave, akhoury, alexpott, ChaseOnTheWeb, Spokje, Wim Leers, aby v a, frob, alison, catch, smulvih2, pameeela, ranjith_kumar_k_u, vsujeetkumar, becassin: Broken "Allowed Tags" updating: after all values for an attribute are allowed, it should not be overridden to allow only certain attribute values

(cherry picked from commit 2aa0817d)