postfix can not start after updating to a newer release, with multiple instance configuration, in Red Hat Enterprise Linux 6

Issue

• /etc/postfix/main.cf was changed wrongly after updating to a newer release of postfix, and postfix service can not start.
• We are using multiple instance configuration in /etc/postfix/main.cf.

multi_instance_wrapper = ${command_directory}/postmulti -p --
multi_instance_enable = yes
multi_instance_directories = /etc/postfix-secondary