emulator: load vendor specific egl libraries first

Unless emulator specifically asks for gpu emulation on the host
(with ro.kernel.qemu.gles set to 1), always try to load vendor
supplied egl libraries on the guest and fall back to software
renderer.

qemu.gles will be setup correctly to reflect what gles is actually
used.

Change-Id: Ibaf2209dd1e40fa9f18ff4df27bb137d7ad53007