There was one instance of BufferVk releasing a buffer it had allocated
from a DynamicBuffer.  This shouldn't have happened as the DynamicBuffer
owns the buffers.

Bug: angleproject:5720
Change-Id: I435512f4bb099130126bf3efb48a238fcd9f3ddb
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2896168
Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org>
Reviewed-by: Mohan Maiya <m.maiya@samsung.com>
Reviewed-by: Jamie Madill <jmadill@chromium.org>