checkout: check if cache.type has changed

[efiop]

Same as in #1370 .

[efiop]

Related to #2358 where we already do that.

For checkout itself, we need to not rely in self.changed()(at least not in its current form, as it doesn't detect link/protected change) in RemoteBASE.checkout() but actually granularly check links. That could be done by modifying changed() so when it sees that self.state doesn't have a correct entry for the path_info, it goes ahead and not only checks the checksums, but also whether or not file is protected and is of correct link type.

[efiop]

Fixed by checkout patch from @pared