Delay instance tagging to later in the instance creation process

Tagging recently created instances can result in
InvalidInstanceID.NotFound errors.

By delaying the tagging until the last part of instance creation,
we should be typically more fortunate (avoiding all such race
conditions might need more work)
Merge pull request #7827 from willthames/delay_tagging_in_ec2

ec2 module: Delay instance tagging to later in the instance creation process