A couple commits got rebased together here, and it's easier to enumerate
them in a single commit.

Skip copying of states during migration if they are the same state. This
can happen when trying to reconfigure a backend's options, or if the
state was manually transferred. This can fail unexpectedly with locking
enabled.

Honor the `-input` flag for all confirmations (the new test hit some
more). Also unify where we reference the Meta.forceInitCopy and transfer
the value to the existing backendMigrateOpts.force field.