[PATCH 1/2] bug fix in ec2::firewall_rule_id

[sang-min . park]

While preparing for the firewall support in eucalyptus driver, I found the bug 
in ec2 driver. 
The issue is 'each_pair' doesn't guarantee that the rule_id string is 
concartenated in the right order.
Specifically I found the prefix and address is switched (e.g., 0, 0.0.0.0).