Add two more parameters to pgxc_ctl.conf

Add two more parameters to pgxc_ctl.conf

pgxc_ctl sets up postgresql.conf and recovery.conf while adding and removing a
coordinator/datanode standby. This interfers with user defined settings if the
user has chosen different mechanism for backup/recovery, such as barman. So
this band-aid fix avoids overwriting the user defined values while
adding/removing standbys. We assume that if these parameters are set to 'y'
(the default is 'n' which means the default old behaviour), then the user would
manually setup things correctly.