LXD test can hang indefinitely

[Rod Smith]

The LXD test can hang indefinitely when trying (but failing) to download an image. The on-screen output looks like this:

DEBUG:root:Executing LXD Test
DEBUG:root:Attempting to initialize LXD
DEBUG:root:Command lxd init --auto:
DEBUG:root: STDERR: LXD has been successfully configured.

DEBUG:root:No local image available, attempting to import from default remote.

Short of rebooting the server, the only solution I could find was to log in using another console or session and kill the lxd process.

I'd like to see a timeout added to the LXD download process so that if it doesn't complete within a reasonable period, the test terminates with a failure and a message about the cause in the results.