Use some of the existing bitmap data to add tests for
qemuBlockBitmapsHandleBlockcopy.

As the output depends on the ordering in the hash table we must also
install the "virdeterministichash" mock preload library.
Signed-off-by: NPeter Krempa <pkrempa@redhat.com>
Reviewed-by: NJán Tomko <jtomko@redhat.com>