mesa/main: fix validation of GL_ANY_SAMPLES_PASSED_CONSERVATIVE

mesa/main: fix validation of GL_ANY_SAMPLES_PASSED_CONSERVATIVE

ctx->Extensions.ARB_ES3_compatibility is set based on the driver-
capabilities, not based on the context type. We need to check against
_mesa_has_ARB_ES3_compatibility(ctx) instead to figure out if the
extension is really supported.

In addition, EXT_occlusion_query_boolean should also allow this
behavior.

This shouldn't cause any functional change, as all drivers that support
ES3_compatibility should in practice enable either ES3_compatibility or
EXT_occlusion_query_boolean under all APIs that export this symbol.

Signed-off-by: Erik Faye-Lund <erik.faye-lund@collabora.com>
Reviewed-by: Tapani Pälli <tapani.palli@intel.com>