Add fog Elasticache security group mocking
Fix Fog::AWS::Elasticache::Mock#authorize_cache_security_group_ingress
Fix for Mock AWS::Elasticache::SecurityGroup deletion
Fixes for comments on pull request

Fog::AWS::Elasticache::Mock.describe_cache_security_groups now has the same method signature as Real and no longer uses opts
Fog::AWS::Elasticache::Mock.create_cache_security_group no longer checks for self.data[:security_groups]
More fixes to AWS::Elasticache mocking

 * Implemented recommendations from @jbence review
 * Enabled tests which revealed a bug in create_cache_security_group response
Another fix from @jbence comments to simplify Excon response in authorize_cache_security_group_ingress
Merge pull request #2082 from sugarb/master

Add fog Elasticache security group mocking