A call to vkBeginCommandBuffer implicitly resets the command buffer.

Bug b/118619338

Change-Id: I020a2d15915cbb309dbcd012b2dbbf34ca2f63c6
Reviewed-on: https://swiftshader-review.googlesource.com/c/23148Tested-by: Alexis Hétu <sugoi@google.com>
Reviewed-by: Chris Forbes <chrisforbes@google.com>
Reviewed-by: Corentin Wallez <cwallez@google.com>