Stop preloading EGL/GLES in Zygote

It's not clear this actually makes much difference on modern
devices/drivers. With updatable graphics drivers, we'd have to be able
to unload the preloaded driver from processes that don't use the
system driver, which is additional complexity and risk.

On bullhead and sailfish, meminfo actually showed slightly more memory
available while sitting at launcher just after boot with this change
than previously. Looking at detailed stats, the differences appeared
to mostly within run-to-run variation, but there wasn't evidence of a
regression.

Bug: 33531483
Test: boot through lockscreen/launcher
Change-Id: I1892302c1750cdbeaf5b9979f8da4dc6bd7b3e75