Update main to get Session Token if profile has no role configured
Update main to get Session Token if profile has no role configured

aws-runas program will now only attempt to Assume Role if the profile
configuration lookup has a role arn.  Otherwise it will fetch session
token credentials instead

mmmorris1975/aws-runas,mmmorris1975/go-aws-runas,mmmorris1975/aws-runas,mmmorris1975/aws-runas,mmmorris1975/aws-runas,mmmorris1975/aws-runas