When an operator does a `find_and_replace` on a DB that already has
shard ranges, they get a prompt like:
This will delete existing 58 shard ranges.
Do you want to show the existing ranges [s], delete the existing
ranges [yes] or quit without deleting [q]?
Previously, if they selected `q`, we would skip the delete but still do
the merge (!) and immediately warn about how there are now invalid shard
ranges. Now, quit without merging.
Change-Id: I7d869b137a6fbade59bb8ba16e4f3e9663e18822
eae27412d2