If the event thread fails, log and restart it with a delay

The event thread should run all the time, or else operations like
internal reboots will fail.

Signed-off-by: David Scott <dave.scott@eu.citrix.com>
If we receive an empty list of events from the backend, log an error

We never want to kill the event thread so we remove the assert.

Signed-off-by: David Scott <dave.scott@eu.citrix.com>
configure: fix the script on OSX

Signed-off-by: David Scott <dave.scott@eu.citrix.com>
Merge pull request #135 from djs55/missing-event-thread

Make the event thread more robust