fw: Provide system context to EnableAccessibilityController.

  Every invocation audit wrapped by AppsOps will validate that the
  original context's uid matches what is being audited. Since we
  create a themed context from system ui, every attempt at flipping
  secure settings while in the GlobalActions scope would lead to
  SecurityExceptions.

  Mitigate by passing original context as well as the themed context
  and constructing the EnableAccessibilityController with the system
  context.

Change-Id: I61d8c99c9da6c7387544c77250907ff4a2ae38d8
TICKET: FEIJ-316