Minor fix to VkWrapTest

We need to make sure we cleanup the VkImage created when testing the
wrapping of a render target.

BUG=skia:

Change-Id: I60ea7e880fecccca309a250cc3b19eb29d6aa89c
Reviewed-on: https://skia-review.googlesource.com/10206
Reviewed-by: Jim Van Verth <jvanverth@google.com>
Commit-Queue: Greg Daniel <egdaniel@google.com>
1 file changed