IAE: Service not registered: com.android.server.AccessibilityManagerService

bug:3331645

1. Let the binder the AccessibilityManagerService has obtained while connecting
   to an accessibility services be garbage collected since when binding we will
   will get in the on #onServiceConnected callback and it can be potentially
   another instance.

Change-Id: I87aa5e5f741e2e54c72d3d0d396ac00eda5aeb5c
diff --git a/services/java/com/android/server/AccessibilityManagerService.java b/services/java/com/android/server/AccessibilityManagerService.java
index 63be030..04ae490 100644
--- a/services/java/com/android/server/AccessibilityManagerService.java
+++ b/services/java/com/android/server/AccessibilityManagerService.java
@@ -685,6 +685,7 @@
          */
         public boolean unbind() {
             if (mService != null) {
+                mService = null;
                 mContext.unbindService(this);
                 mComponentNameToServiceMap.remove(mComponentName);
                 mServices.remove(this);