Adds support for purge_rules. Similar to how ec2_elb_lb does with zones

cloud/ec2_group

@@ -45,6 +45,20 @@ options:
     default: 'present'
     choices: [ "present", "absent" ]
     aliases: []
+  purge_rules:
+    version_added: "1.7"
+    description:
+      - Purge existing rules on security group that are not found in rules
+    required: false
+    default: 'true'
+    aliases: []
+  purge_rules_egress:
+    version_added: "1.7"
+    description:
+      - Purge existing rules_egree on security group that are not found in rules_egress
+    required: false
+    default: 'true'
+    aliases: []
 
 extends_documentation_fragment: aws
 
@@ -164,6 +178,9 @@ def main():
             rules=dict(),
             rules_egress=dict(),
             state = dict(default='present', choices=['present', 'absent']),
+            purge_rules=dict(default=True, required=False, type='bool'),
+            purge_rules_egress=dict(default=True, required=False, type='bool'),
+
         )
     )
     module = AnsibleModule(
@@ -177,6 +194,8 @@ def main():
     rules = module.params['rules']
     rules_egress = module.params['rules_egress']
     state = module.params.get('state')
+    purge_rules = module.params['purge_rules']
+    purge_rules_egress = module.params['purge_rules_egress']
 
     changed = False
 
@@ -274,6 +293,7 @@ def main():
                     changed = True
 
         # Finally, remove anything left in the groupRules -- these will be defunct rules
+        if purge_rules:
             for rule in groupRules.itervalues() :
                 for grant in rule.grants:
                     grantGroup = None
@@ -338,6 +358,7 @@ def main():
                 del groupRules[default_egress_rule]
 
         # Finally, remove anything left in the groupRules -- these will be defunct rules
+        if purge_rules_egress:
             for rule in groupRules.itervalues():
                 for grant in rule.grants:
                     grantGroup = None