Medium: RA: portblock: fix invalid exit codes on monitor

IptablesStatus() returns 1 ($OCF_ERR_GENERIC) whenever the
iptables rule is not configured. This breaks probes whenever a
resource which is expected to be stopped, is in fact stopped.

Also, this patch removes a pointless function wrapper and uses
$OCF_RESOURCE_INSTANCE for the ha_pseudo_resource state file
name.

This updated patch also removes another obsolete comment.