commit: Add 'base' to the reopen queue before 'overlay_bs'

Now that we're checking for duplicates in the reopen queue, there's no
need to force a specific order in which the queue is constructed so we
can revert 3db2bd5508c86a1605258bc77c9672d93b5c350e.

Since both ways of constructing the queue are now valid, this patch
doesn't have any effect on the behavior of QEMU and is not strictly
necessary. However it can help us check that the fix for the reopen
queue is robust: if it stops working properly at some point, iotest
040 will break.

Signed-off-by: Alberto Garcia <berto@igalia.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
