Vulkan: Fix trace behavior of vkCmdCopyBufferToImage.
Vulkan: Fix trace behavior of vkCmdCopyBufferToImage.

The temporary variables for these slices apparently change the trace behavior of
vkCmdCopyBufferToImage and vkCmdCopyImageToBuffer, causing some applications to
hang when tracing.

google/gapid,google/gapid,Qining/gapid,google/agi,google/gapid,google/agi,pmuetschard/gapid,google/agi,pmuetschard/gapid,Qining/gapid,pmuetschard/gapid,google/gapid,google/gapid,Qining/gapid,Qining/gapid,google/gapid,google/agi,google/gapid,pmuetschard/gapid,pmuetschard/gapid,pmuetschard/gapid,google/gapid,Qining/gapid,pmuetschard/gapid,google/agi,google/agi,google/agi,Qining/gapid,google/agi,Qining/gapid,Qining/gapid,pmuetschard/gapid