The issue occurs that binds the same buffer and calls glDrawElements
with the same indices. The offset has been reset in the
VertexArrayVk::syncState(), but it doesn't check the actual value
in the ContextVk::setupIndexedDraw().
Also corrected case where update via BufferSubData wasn't being
sent to the HW.

Bug: angleproject:3362
Change-Id: I0f7d2fc162bc8f1c36cb09ba689fd27b482b9035
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1666345
Commit-Queue: Courtney Goeltzenleuchter <courtneygo@google.com>
Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>