It is illegal to start a new draw operation while a transform
feedback is active.

Change-Id: I5ebb01889ce5154162a51f5e6cfbc8431554c879
Reviewed-on: https://swiftshader-review.googlesource.com/3549Tested-by: Alexis Hétu <sugoi@google.com>
Reviewed-by: Nicolas Capens <capn@google.com>