services: don't clear wallpaper when SystemUI
disconnects.

When we restart SystemUI (or the user), sometimes
the wallpaper would get cleared. This patch just
captures its originating component and
if that is our SystemUI component, ignore the event.

Change-Id: I3e159dc2c013e7d7e552e3c0cef55e3ab970ca87
Signed-off-by: Roman Birg <romanbirg@gmail.com>
Allow USB notification to show when primary SD allows UMS and MTP

Previously if primary SD is set to allowMassStorage="true" the USB
dialog would never show.  This checks if persist.sys.usb.config is
set to mtp,adb and then allows the USB notification to show. With
this you can then have the option to select from MTP, PTP and Mass
storage when clicking the pull down notification. When Mass Storage
is selected it activates the USB connected dialog to turn on USB
storage. When set back to MTP the USB connected notification disappears.

Change-Id: I2287075ec93cae75f19e8fb59965d9dddb234aca