When there's multiple transactions in the queue, sway can take a
shortcut by checking if they all operate on the same set of containers.
If they do, it can skip all but the last transaction. The way we tested
for transactions which used the same containers was to exclusive-or
their con IDs together, but this has proved not only to be ineffective
but also has the potential to make sway crash.
This patch replaces the exclusive-or with a loop and container
comparison.
b12f7be907