Output different error for when CL cannot be created in canary task driver

Bug: skia:10477
Change-Id: I46a48185977a409225583aea58f5fd31cf306d4c
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/303266
Reviewed-by: Eric Boren <borenet@google.com>
Commit-Queue: Ravi Mistry <rmistry@google.com>
1 file changed