remote: in per-driver daemons ensure that state initialize succeeds

remote: in per-driver daemons ensure that state initialize succeeds

When running in libvirtd, we are happy for any of the drivers to simply
skip their initialization in virStateInitialize, as other drivers are
still potentially useful.

When running in per-driver daemons though, we want the daemon to abort
startup if the driver cannot initialize itself, as the daemon will be
useless without it.

Reviewed-by: Andrea Bolognani <abologna@redhat.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>