xenconsoled: improve robustness of logfile handling

xenconsoled: improve robustness of logfile handling

Check the 'log_reload' on every iteration of the select() loop, not just when
select() returns EINTR. This is because the log reload signal may have
iterrupted a syscall other than select & thus without this change  we
might miss the reload signal.  The second change makes us process the
hypervisor logs on every iteration of the loop, not just upon timeouts.
This is because if a guest VM were consistently sending some log message
and < 1 second period, the select() would never hit the 1 second timeout
and thus never process the HV logs.

Thanks to Markus Armbruster for pointing out both these edge cases

Signed-off-by: Daniel P. Berrange <berrange@redhat.com>