This reverts commit 9aa865a6.

Reason for revert: Seems to be causing crashes on Android in glmark2.
Might also be responsible for a perf regression.

Bug: angleproject:3542

Original change's description:
> Vulkan: Add missing command pool reset.
> 
> We were still calling destroy in checkCompletedCommands. We can
> instead call reset.
> 
> May not significantly impact performance.
> 
> Bug: angleproject:3489
> Change-Id: I61a2cb154faac56dc78a49678dd822d81ce16ad2
> Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1647029
> Reviewed-by: Jamie Madill <jmadill@chromium.org>
> Reviewed-by: Tobin Ehlis <tobine@google.com>
> Commit-Queue: Jamie Madill <jmadill@chromium.org>

TBR=tobine@google.com,jmadill@chromium.org

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: angleproject:3489
Change-Id: Icb0e99f18ecab09798654605973958bd2b263002
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1665748Reviewed-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Cody Northrop <cnorthrop@google.com>
Commit-Queue: Jamie Madill <jmadill@chromium.org>