Revert "VolumePanel: Fix Theme Engine support with On-The-Spot dialog"

This reverts commit 09df5f71d13659cda5a83e4369b9c81bf4116ece.
Themes: Full support for AOSP Volume Panel

- Recreate VolumePanel with theme enegine UiContext.
- Revert this https://gerrit.paranoidandroid.co/#/c/4375/ since we don't have
  the code with the panel they refer to. Just leave UiContext commented out, maybe
  we'll need that lately.

Signed-off-by: Carlo Savignano <stevewatersy@gmail.com>
Change-Id: Ifc9fd02ec4d263050b7d5f689935fa5e82095d26
VolumePanel: Fix Theme Engine support with On-The-Spot dialog

Our on the spot feature needs to write to system. Since VolumePanel when is
recreated uses theme engine context (and in this case is fked), pass to on the spot dialog always the
first system initialized one. Thanks to @David96 helping find this out :)

This way we lose theming for the safe headset on the spot dialog,
but we're already finding a really good fix, we have something already :)

Fix AOSPA-482

Signed-off-by: Carlo Savignano <stevewatersy@gmail.com>
Change-Id: I492cd8e24b09d856d23697b84113664379703cf1
Conflicts:
	core/java/android/view/VolumePanel.java

Conflicts:
	media/java/android/media/AudioService.java