We were comparing a pre-promotion version with the post-promotion
version stored in the share context. This doesn't work.

Affects: dEQP-EGL.functional.sharing.*

Change-Id: I02c14681b7743c6aaef4404291ac52a48890832c
Reviewed-on: https://swiftshader-review.googlesource.com/20368Tested-by: Chris Forbes <chrisforbes@google.com>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>