Another pass reviewing code:

- remove a duplicate check for ssh connection and just exit if
  we can't connect to the remote host.
  stop_backup is only needed if pg_start_backup() has been
  already called
- remove a new connection to master in stop_backup label, AFAIC
  we hadn't close the one we already opened
- add a lot of PQfinish(), a few PQclear() and adjust code to what
  we used to do in 1.x

errcode.h

@@ -34,5 +34,6 @@
 #define ERR_BAD_PASSWORD 9
 #define ERR_STR_OVERFLOW 10
 #define ERR_FAILOVER_FAIL 11
+#define ERR_BAD_SSH	12
 
 #endif	/* _ERRCODE_H_ */