txn: remove recovery vclock promotion from recovery_fill_lsn()

* promote recovery vclock in recover_xlog(), after we apply
  the recovered row
* remove unnecessary promotions from WAL and relays: they
  should not use recovery vclock going forward.
* update format specifier for error code ER_UNKNOWN_REPLICA
  to expect a string, rather than integer, since it's passed
  a string for replica id, not integer
* remove unused code in relay.cc