empty folders cannot be deleted with `delete` command

[andynog]

Currently if a folder is empty e.g. cosmos/ceph-cosmos if you issue a command multisig delete cosmos ceph-cosmos the command doesn't delete the folder, in order to remove it you need to execute two raw delete commands: multisig raw delete cosmos/ceph-cosmos/ multisig raw delete cosmos/

It would be nice if the delete command would get rig of the folder (sometimes the folder created was with an invalid chain-id or key name).