Make sure we wait to call finishedCallback in vk setBackendSurfaceState.

Bug: b/189671648
Change-Id: Iae04853184a5fe12459469db5e129db0cb5719a5
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/414520
Auto-Submit: Greg Daniel <egdaniel@google.com>
Commit-Queue: Jim Van Verth <jvanverth@google.com>
Reviewed-by: Jim Van Verth <jvanverth@google.com>
2 files changed