Fix passing an instance profile arn to ec2_launch_template

If the string given on the iam_instance_profile looked like an arn, the
wrong structure format was being returned. boto3 expects a dict of the
format { arn: "{{ arn }}" } but the string was returned instead.

This fixes this error:
Couldn't create subsequent launch template version: Parameter validation failed:
Invalid type for parameter LaunchTemplateData.IamInstanceProfile, value: arn:aws:iam::[...]:instance-profile/[...], type: <class 'str'>, valid types: <class 'dict'>

plugins/modules/ec2_launch_template.py

@@ -384,7 +384,7 @@
 
 def determine_iam_role(module, name_or_arn):
     if re.match(r'^arn:aws:iam::\d+:instance-profile/[\w+=/,.@-]+$', name_or_arn):
-        return name_or_arn
+        return {'arn': name_or_arn}
     iam = module.client('iam', retry_decorator=AWSRetry.jittered_backoff())
     try:
         role = iam.get_instance_profile(InstanceProfileName=name_or_arn, aws_retry=True)