Degrading epoll errors in vmchannels to log level INFO

Error events from epoll are quite common due to lost connections
on shutdown, migrations or suspension of VMs, since this is not
a critical error the message gets degraded to INFO.

Change-Id: I0099fb39a6261e2339c12ae25ea16f32bff1a55f
Bug-Url: https://bugzilla.redhat.com/1102549
Signed-off-by: Vinzenz Feenstra <vfeenstr@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/30141
Reviewed-by: Francesco Romani <fromani@redhat.com>
Reviewed-by: Martin Polednik <mpolednik@redhat.com>
Reviewed-by: Dan Kenigsberg <danken@redhat.com>