[bug 1111265] Restrict remote-troubleshooting to Firefox

If there's a mismatch between the product the user is leaving feedback
about and the browser the user is using, then we really don't want the
browser data. I haven't figured out how to programmatically figure that
out in a general way, yet.

In the meantime, we're going to restrict this to Firefox product only
because that's where we get the best bang for our buck right now anyhow.
Merge pull request #414 from willkg/1111265-restrict-remote-t

[bug 1111265] Restrict remote-troubleshooting to Firefox