ec2.Instance allows cloudformation Tag instances.

I erroneously set my tags to be cloudformation tags:

from troposphere.autoscaling import Tag
instance = ec2.Instance(...)
instance.Tags = [ Tag(...) ]

And...neither the `instance.validate()` nor the Template that I added it to complained - I would have expected some kind of complaint along the lines of 'Tags list may only contain instances of ec2.Tag'.

The issue identifies ec2.Instance.Tags and the autoscaling.Tag and ec2.Tag classes as the entry points. Compare how tag validation is performed during instance.validate() and Template validation, then add regression coverage showing that an autoscaling Tag is rejected where an ec2.Tag is required.

Written by the indexing model from the issue text.