Fix SmartState Analysis failures on non-English VMs.

Text retrieved from non-English Windows VMs may be encoded in
UTF-16. This text may contain byte sequences that are not valid
in UTF-8. Check the text for valid encoding, and convert to UTF-8
as needed.

https://bugzilla.redhat.com/show_bug.cgi?id=1126476
Fixes #293
Fixes #332