NsdService does not clean up after exiting clients

When a client of the NsdService exits, NsdService should
clean up the requests it has sent to the mDNS daemon:
cancel any pending resource-discovery and resource-resolution
queries, and remove any services registered by this client.

If this isn't done, several bad things happen. The daemon will
continue to run unnecessarily, will report service discoveries
that can't be forwarded on to the client, and will continue to
advertise service ports for an application which is no longer
running until the device is rebooted (mDNS pollution).

Bug: 9801184
Change-Id: I0aa7311480322aefcff16f902fbbf34f50985d38
NULL previous background bitmap upon changing wallpaper

Step to reproduce it on Nexus 10 with 4.4.2(KOT49H):
1. Long press on home screen.
2. Choose wallpaper from Wallpapers.
3. Select new wallpaper and set it.
4. Repeat step 1-3 several times.
See black background instead of the wallpaper.

There are two binder objects who hold reference to the
ImageWallpaper$DrawableEngine, which keeps the big chunk
bitmap from being recycled.
One is WallpaperService$IWallpaperEngineWrapper. The client
references went away slowly, maybe several minutes after
changing wallpaper. Then the finalizer has to been executed
to GC it.
The other one is WallpaperService$Engine$BaseIWindow. Don't
know who still held reference to it even after the window
was removed.
Anyway, let the bitmap be GCed first.

Change-Id: I27f6971a3edd26472b69e59b542b27fd7c8e7b90
Signed-off-by: jshe32X<jianchunx.shen@intel.com>
Signed-off-by: Guobin Zhang <guobin.zhang@intel.com>
remove unnecessary switchUser call

If userId doesn't change, no need to do switchuser.or it will
introduce some tweak for gps modules in quick off/on because
they need cost time in off/on.

Change-Id: Ie5e408dc8be69c8a63a18bcb2cfe478cef4d70e6
Signed-off-by: Jianzheng Zhou <jianzheng.zhou@freescale.com>