Return the right error code when trying to move an item that doesn't exist

Summary:
We used to return 110, which is not a valid code for MoveItems, now we return 1 as we
should.
We now also prefer the "invalid source collection" error code to the
"source and destination are equal" code. This is because if we have
garbage as source and destination, it makes more sense to say that the
id is invalid then that it is equal.

Differential Revision: https://git.kolab.org/D4950