Fix deadlock between DPMS and AMS

Fixing deadlock between DevicePolicyManagerService and
AccessibilityManagerService.

(HOLD_AMS_LOCK)AMS.isAccessibilityTargetAllowed - > DPMS.getPermittedAccessibilityServicesForUser(WAIT_FOR_DPMS_LOCK)

(HOLD_DPMS_LOCK)DPMS.dump -> AMS (WAIT_FOR_AMS_LOCK)

Bug: 284777986
Test: NA
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:058ebf6e40b38333a7419ebde40d16518dba0637)
Merged-In: I0aa2e397ac49d90b5f89ba10e11cab665cc2e915
Change-Id: I0aa2e397ac49d90b5f89ba10e11cab665cc2e915