The "Ragnarok M: Eternal Love" game uncovered a bug where 2 contexts
shared a VkCommandBuffer.  The one context was used by one thread for
rendering, and the other context/thread dispatched compute shaders.
When the rendering thread destroyed a VkCommandBuffer, future compute
dispatches crashed because the new VkCommandBuffer didn't have a
compute pipeline bound.

Bug: b/181711029
Change-Id: I8bc85150c1c6202e02feb84a7ccc0ad7b9c39258
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2770681
Commit-Queue: Ian Elliott <ianelliott@google.com>
Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>