Overcloud stack update failed after enabling TLS on public endpoints.

Issue

• Attempt was made to enable SSL on public endpoints and the update got stuck and eventually fails with the below error:

  2019-08-08 14:33:14Z [Controller]: UPDATE_FAILED  UPDATE aborted (Task update from ResourceGroup "Controller" [4731babf-5030-4ab2-801a-ecc68df312e7] Stack "overcloud" [2951215d-212d-4fcf-8798-fa57b0ba6ca3] Timed out)
  2019-08-08 14:33:14Z [overcloud-Controller-t2nbvenmadk6]: UPDATE_FAILED  Stack UPDATE cancelled
  2019-08-08 14:33:15Z [overcloud]: UPDATE_FAILED  Timed out
  2019-08-08 14:33:15Z [overcloud-Controller-t2nbvenmadk6-0-t6kksrvkz54s]: UPDATE_FAILED  Stack UPDATE cancelled
  2019-08-08 14:33:15Z [overcloud-Controller-t2nbvenmadk6.0]: UPDATE_FAILED  resources[0]: Stack UPDATE cancelled
  2019-08-08 14:33:15Z [overcloud.Controller]: UPDATE_IN_PROGRESS  state changed
  2019-08-08 14:33:15Z [overcloud-Controller-t2nbvenmadk6]: UPDATE_FAILED  Resource UPDATE failed: resources[0]: Stack UPDATE cancelled
  
   Stack overcloud UPDATE_FAILED
  
  Heat Stack update failed.
  Heat Stack update failed.