Unlocking a previous deployment makes pacman database incoherent

One can end up in a state where pacman has a database not relevant to the current deployment and can break the system.

Steps to reproduce:
1. start with a locked image
2. deploy another image
3. boot the old image
4. unlock that one
5. boot the new deployment

Option two:
1. start with a locked image
2. deploy another image
3. unlock the currently-running image
4. boot the new deployment

The result will be a locked deployment that has the pacman database of the older image. Attempting to update the system breaks it. Attempting to install a package will install something that might not work due to needed libraries not being ABI-compatible.