use new name for new format content identifier db

It will be populated automatically by the next command that needs data
from it, the same way it gets populated in a fresh clone. That may be a
little expensive, but it's a one time cost, and no slower than in a
fresh clone.

Annex/Locations.hs

@@ -375,7 +375,7 @@ gitAnnexExportExcludeLog u r = gitAnnexDir r </> "export.ex" </> fromUUID u
  - need to be rebuilt with a new name.)
  -}
 gitAnnexContentIdentifierDbDir :: Git.Repo -> FilePath
-gitAnnexContentIdentifierDbDir r = gitAnnexDir r </> "cids"
+gitAnnexContentIdentifierDbDir r = gitAnnexDir r </> "cidsdb"
 
 {- Lock file for writing to the content id database. -}
 gitAnnexContentIdentifierLock :: Git.Repo -> FilePath