OPENTOK-17941 #comment Because... when a configuration change happens, t...

...he subscriberview removal is immediate, and the subscriberview re-addition is delayed... it's possible to have remove/remove/add/add ordering instead of remove/add/remove/add when two config changes happen quickly (which seems to be possible when iOS is on the other side of the connection).  You add twice in a row, you crash.  So we'll do a harmless (hopefully) redundant remove before we re-add the subscriber view