Fix error reporting in Surface::cancelBuffer()

when we validate the surface there, most errors are in fact allowed
because it is legal to cancel a buffer after a surface has been
destroyed (for instance). in that case make sure to not log
error messages as they are very confusing.

Change-Id: Iecdfbaf6d9ee5da54d56cd7ea7a0d430c30934b0
2 files changed