[clients] resolve inconsistent state in redis
[clients] resolve inconsistent state in redis

I'm not sure exactly what can cause this state to occur, but it's
possible for sensu to have a client name in the clients list that does
not have a paired `client:` config.

When this happens, the api server restarts/crashes every time you hit
`/clients/`.

crewton/sensu,solarkennedy/sensu,roobert/sensu,cread/sensu,yonglehou/sensu,upfluence/sensu,m4ce/sensu,portertech/sensu,somic/sensu,miyakawataku/sensu,rbramwell/sensu,bf4/sensu,keymone/sensu,npe9/sensu,sensu/sensu