bug: IAM manager doesn't update trusts when multiple service accounts listed.

[kevdowney]

Is this a BUG REPORT or FEATURE REQUEST?:
BUG
What happened:
When more then one irsa-service-account is listed the trust only picks up the last one.

apiVersion: iammanager.keikoproj.io/v1alpha1
kind: Iamrole
metadata:
  annotations:
    iam.amazonaws.com/irsa-service-account: default,my-service-account

We see in the IAM Role trusts only the last one is updated:

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Effect": "Allow",
            "Principal": {
                "Federated": "arn:aws:iam::1234567890:oidc-provider/oidc.eks.us-west-2.amazonaws.com/id/EC888888xxxxxxx"
            },
            "Action": "sts:AssumeRoleWithWebIdentity",
            "Condition": {
                "StringEquals": {
                    "oidc.eks.us-west-2.amazonaws.com/id/EC888888xxxxxxx:sub": "system:serviceaccount:my-namespace:my-service-account"
                }
            }
        }
    ]
}

What you expected to happen:

• 2 trusts should be entered for IAM Role, one for default and one for my-service-account

How to reproduce it (as minimally and precisely as possible):

Anything else we need to know?:
This PR introduced this behavior, but doesn't handle multiple similar conditions.
We can just change the Id() method to handle condition, making sure we dereference as string.

Environment:

• iam-manager version
• Kubernetes version :

$ kubectl version -o yaml

Other debugging information (if applicable):

- controller logs:

$ kubectl logs