Revert "Make incall screen glopad background themeable"

Change I6a0a120662e4e45b5282a763c8ccf41d29c6d470 was supposed
to make only bottom half of caller photo semi-transparent. Instead
it also exposes in-call buttons at the bottom of the screen behind
the glowpad. This has looked plain broken for months.

This reverts commit 3073f8760c82198a80cf8efe3fe0e3b2804852c2.

Change-Id: I38d2b8aefdaa77385c863b97221e88f0da6a97e2