Dependencies between security groups

[pauldraper]

Adding two security groups, one which references the other:

$ cumulus security-groups sync
creating us-east-1/aws-api...
    adding inbound rules...
        No such security group: elb-aws-api. Security group not added.
creating us-east-1/elb-aws-api...
    adding inbound rules...
$ cumulus security-groups sync
updating us-east-1/aws-api...
    adding inbound rules...

Rerunning twice fixes it. Not a high priority fix. (Though it does become more complicated if they referenced each other.)