Removes unused code from the SystemServer/Zygote classes.

This patch partially reversts ag/6991475 and ag/7161709.  These changes
are no longer needed due to a change in the graphics driver strategy for
Q.

In addition, the preloading of the graphics driver in the USAPs need to
be removed to avoid causing a memory regression on devices with graphics
driver preloading in the Zygote disabled.

Bug: 134526352
Test: Treehugger
Change-Id: I570037866d1ae90794c711622e6045ebbffa5b9c
Merged-In: I570037866d1ae90794c711622e6045ebbffa5b9c
(cherry picked from commit fcd68fd7)