Facter can't handle non-ascii ec2_userdata

If we try to use Puppet 3.7.4/Facter 2.2.0 on Amazon Linux provisioned by Ops Works, we see the following error:

Fact resolution fact='ec2_userdata', resolution='rest' resolved to an invalid value: String encoding ASCII-8BIT is not UTF-8 and could not be converted to UTF-8

It appears to be the gzipped userdata causing the issue.

ec2_userdata is an Advanced option when creating an EC2 instance. You can specify either text or a file. If the file is compressed - which is one way to get around the 16KB file limit for userdata - it will produce a warning. This is a common case that we can't handle generically (because the file can be any format), so it makes sense to ignore non-text and log a debug message.