Low: pgsql: add a function to retry command
Low: pgsql: change name and specification of exec_func_with_timeout

- change function name from exe_func_with_timeout to exe_with_timeout
- change specification of exe_with_timeout to conform it to exec_with_retry
- exe_with_timeout outputs more logs
- increase in performance
Low: pgsql: Share output of crm_mon. If crm_mon fails, RA re-exec it
Low: pgsql: improve error handling of crm_xxxx commands

retry executing crm_xxxx commands if they fail
because the number of IPC connections reaches maximum,
crm_xxxx commands fail.
Low: pgsql: simplify picking out data status
Medium: pgsql: set only one node into sync mode when using 3 nodes or higher

Only one node can be sync mode to avoid data loss when using 3 nodes or higher.
See http://www.gossamer-threads.com/lists/linuxha/pacemaker/85077?do=post_view_threaded#85077
Low: pgsql: remove unnecessary code which is used by multiple synced nodes
Low: pgsql: re-control slave status when sync mode is changed

execute control_slave_status() once again to improve performance
of catching up slave status.