[1.7.x] Fixed bug in circular dependency algo for migration dependencies.

Previous algo only worked if the first item was a part of the loop,
and you would get an infinite loop otherwise (see test).

To fix this, it was much easier to do a pre-pass.

A bonus is that you now get an error message that actually helps you debug
the dependency problem.

Backport of ff3d746e from master, with
additional tests from c5def493