When disconnecting a surface, cancel don't queue the buffer

This isn't really right either, but avoids having an extra buffer that
the consumer has to drain which it might not be expecting.

To be correct, disconnecting a surface from a context should retain
the current buffer and continue using it when reconnected. The buffer
should only be canceled when the surface is destroyed. That will wait
for a later change.

Bug: 8320762
Change-Id: I5efa39c741193ca4f5612ea9de001ccbb683b345