Add IAM role filters

[svenwltr]

Add additional filters to prevent errors like that:

eu-west-1 - IamRolePolicyAttachement - 'AWSServiceRoleForEC2Spot -> AWSEC2SpotServiceRolePolicy' - UnmodifiableEntity: Cannot perform the operation on the protected role 'AWSServiceRoleForEC2Spot' - this role is only modifyable by AWS
	status code: 400, request id: 5dce7817-d02c-11e7-a395-9be537ee44f3
eu-west-1 - IamRolePolicyAttachement - 'AWSServiceRoleForEC2SpotFleet -> AWSEC2SpotFleetServiceRolePolicy' - UnmodifiableEntity: Cannot perform the operation on the protected role 'AWSServiceRoleForEC2SpotFleet' - this role is only modifyable by AWS
	status code: 400, request id: 5e5c38ec-d02c-11e7-821c-d1b97041f7ca
eu-west-1 - IamRolePolicyAttachement - 'AWSServiceRoleForOrganizations -> AWSOrganizationsServiceTrustPolicy' - UnmodifiableEntity: Cannot perform the operation on the protected role 'AWSServiceRoleForOrganizations' - this role is only modifyable by AWS
	status code: 400, request id: 5e9f83c1-d02c-11e7-a395-9be537ee44f3
us-east-1 - IamRolePolicyAttachement - 'AWSServiceRoleForEC2Spot -> AWSEC2SpotServiceRolePolicy' - UnmodifiableEntity: Cannot perform the operation on the protected role 'AWSServiceRoleForEC2Spot' - this role is only modifyable by AWS
	status code: 400, request id: 5f45393a-d02c-11e7-a972-a1e741747b1a
us-east-1 - IamRolePolicyAttachement - 'AWSServiceRoleForEC2SpotFleet -> AWSEC2SpotFleetServiceRolePolicy' - UnmodifiableEntity: Cannot perform the operation on the protected role 'AWSServiceRoleForEC2SpotFleet' - this role is only modifyable by AWS
	status code: 400, request id: 5f86fd7b-d02c-11e7-b57f-af3e065a40e2
us-east-1 - IamRolePolicyAttachement - 'AWSServiceRoleForOrganizations -> AWSOrganizationsServiceTrustPolicy' - UnmodifiableEntity: Cannot perform the operation on the protected role 'AWSServiceRoleForOrganizations' - this role is only modifyable by AWS
	status code: 400, request id: 5fcbf624-d02c-11e7-b57f-af3e065a40e2

Removal requested: 0 waiting, 7 failed, 59 skipped, 2 finished

Error: There are resources in failed state, but none are ready for deletion, anymore.

@rebuy-de/prp-aws-nuke Please review.