EC2 Windows Bootstrap patch: Added test function to check for winrm read...

knife command:  knife ec2 server create --bootstrap-protocol winrm -d windows-chef-client-msi [....]
Please review this pull request as it fixed the case where running the command above with all other parameters resulted in knife-ec2 prematurely running bootstrap commands when winrm wasn't ready to accept requests.

This was the missing piece I needed to get "knife-ec2" to play nice with knife-windows in EC2.