Recover current view from state after SST.

When member joins the group and needs to receive an SST it won't
receive the corresponding menbership view event because the SST
happens after the event and will already include the effects of
all events ordered before it. The view then must be recovered from
the received state.

Minor renames and cleanups.

References codership/wsrep-lib#18

dbsim/db_client.hpp

@@ -59,6 +59,7 @@ namespace db
         { }
         void start();
         wsrep::client_state& client_state() { return client_state_; }
+        wsrep::client_service& client_service() { return client_service_; }
         bool do_2pc() const { return false; }
     private:
         friend class db::server_state;