Fixes#517.
The problem was that again, only the `vercode`s of apks were being
compared to see if they were the same, rather than `vercode` and `id`.
The result is that some new apks will incorrectly be asked to execute
an `UPDATE` query rather than an `INSERT`. As such, they don't end
up in our database at all because the `UPDATE` will not run against
any row at all.