Start PostgreSQL as Hot Standby and check wal_receiver process

I improved my patches.
ref : https://github.com/ClusterLabs/resource-agents/pull/187
idea : https://github.com/t-matsuo/resource-agents/wiki/Resource-agent-for-postgresql-9.2-for-disaster-site


I added new option to start PostgreSQL as Hot Standby.
- rep_mode=slave starts PostgreSQL as Hot Standby to connect to Primary.
- add check_wal_receiver parameter which check wal receiver process
  and notify its status using attribut to check connection.