Touch exploration gesture end not delivered to clients.

1. Touch exploration gestures are demarcated by start and end
   events. Due to a bug in the AccessibilityManagerService
   the gesture end event was not dispatched. This caused the
   AccessibilityNodeInfoCache to be off sync since it relies
   on getting such events not to mention that the clients were
   not getting the end but only the start event. The issue
   was that the notified service types variable was not reset
   after every event so when the manager sends the last hover
   exit it flags that the service type is already notified
   resulting in dropping on the floor the following gesture
   end event.

bug:6539306

Change-Id: I2b96bcecea3b2240199d67f01afa6a033afce1de