Add logging to metadata parsing

The TaggedAttachmentsTest class queries server metadata to see if the
tagging is visible from the guest. However when the check fails it does
not log what was the faulty metadata. To make troubleshooting easier
this patch adds logging for the error cases.

Change-Id: I58f6fefef0f0a9db2f7fdf2a1a0125f616319949
1 file changed