frameworks/base: Fix for UI freeze issue with headset insert/removal

- UI freeze is observed while quick insertion and removal of headset
  for multiple times.
- notifyJackSwitchChanged() acquires mHeadsetLock and waits on
  phoneWindowManager lock to call update() as it is a synchronized
  function. sendIntents() is also "synchronized". This function also
  tries to acquire mHeadsetLock. So there is a dead lock, when the
  notifyJackSwitchChanged() acquires the mHeadsetLock before this
  function does.
- update() is called only from notifyJackSwitched() and need not be a
  synchronized function. Removed synchronization on the update() to
  fix the issue.

CRs-Fixed: 390784
(cherry picked from commit 04e683e79c3633e061c71b2ecff4f4c83624d1e0)

Change-Id: I6d274391b68c0a306128d7009bbb651a9b0554f4