Update UC example to allow role to assume-itself

[hectorcast-db]

Update UC example to allow role to assume-itself

[alexott]

In general looks good, was it tested somewhere? I don't have environment to test right now

[hectorcast-db]

@yuchenhuo @alexott I just tested creating the policy and role from the example. My understanding is that the condition is required if you want to add permissions in the assume_role_policy, but not for the permission policy itself. This is because the role in the assume_role_policy must exist at creation time, so we get a chicken and egg problem.

But using assume_role_policies, seems a better choice. Let me try to rewrite this.