Console: prefix the paths read with the frontend directory

Signed-off-by: David Scott <dave.scott@eu.citrix.com>
Ignore duplicate notifications of domains arriving/leaving

The DomainWatch `Destroyed event can trigger multiple times, once
per internal state change of the domain. Perhaps the events should
be filtered and only occur once per domain?

Signed-off-by: David Scott <dave.scott@eu.citrix.com>