Clean up egl_connection_t::shouldUseAngle

If android::GraphicsEnv::getInstance().shouldUseAngle() returns false,
then the ANGLE driver loading can bail out early. The choice should be
made before the app starts loading the driver. If there's a change in
the driver choice during driver loading, then it shouldn't affect the
current loading process, but the next app fresh launch, otherwise crash
will happen for the 3-part driver loading.

Test: build
Change-Id: I9ea202214bdbc4b70d068137c62d2b1f8ac8ebb5