Sometimes EC2 response to security group actions is failure, but the action succeeds.  This fix catches and ignores the errors.
Merge pull request #303 from briandrawert/retry-auth-on-ec2-security-groups2

Retry auth on ec2 security groups
adding in a sleep before starting appscale on instances in euca to let EBS volumes attach successfully
added comment explaining sleep statement
Merge pull request #307 from shatterednirvana/sleep-on-euca

Sleep on euca to allow EBS volumes to get attached