[COOK-3785] updated to include link to init script.
Add centos and amazon to redhat platform block.
DRY up supervisord.init template for redhat, centos, and amazon.
Fix up attribution.
Tweak rhel init script: add echo statement and change default return value.
Fix exit status of "/etc/init.d/supervisord status" under rhel.

Prior to this change, under CentOS for example, the service[supervisord]
resource could think that supervisord was running even when it wasn't.
This is because under CentOS (and possibly other platforms), "supervisorctl
status" exits with status 0 even when supervisord is not running:

    $ supervisorctl status
    unix:///var/run/supervisor.sock no such file
    $ echo $?
    0
Make sure total_sleep is initialized.
Add amazon, centos, and redhat to metadata.rb's supports.
DRY up calls to supervisorctl status.
Return exit status of zero if starting when already started.
Merge branch 'cook-3785-support-rhel-family' into develop

Conflicts:
	recipes/default.rb
	templates/default/rhel_supervisord.init.erb