If the WAL receiver has been temporarily disabled, we don't want to
wait for it to start up as it may not be able to at that point; we do
however need to reset "wal_retrieve_retry_interval".
This is intended to ensure that all nodes have a constant LSN while
making the failover decision.
This feature is experimental and needs to be explicitly enabled with the
configuration file option "standby_disconnect_on_failover".
Note enabling this option will result in a delay in the failover decision
until the WAL receiver is disconnected on all nodes.
