There was a lot of similarity between the bankd_client_fsm (for the
client->bankd RSPRO connection) and the rspro_client_fsm (for the
client->server and the bankd->server RSPRO connections).
With the last few commits introducing the missing features to
rspro_client_fsm, we can completely obsolete bankd_client_fsm and
further simplify the codebase.
Change-Id: Icbe9881a0391fcd0c47e5d930dc764fc0cb1dfbf