vm: promote some debug messages to info

Promote to 'info' some logs which
are high level and important enough to deserve it.

This patch is part of the preparation for
the switch to default log level to 'info'
in VDSM.

Change-Id: I46621bd4e3c800f58c4269e5d5c86499839bd029
Signed-off-by: Francesco Romani <fromani@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/34355
Reviewed-by: Vinzenz Feenstra <vfeenstr@redhat.com>
Reviewed-by: Dan Kenigsberg <danken@redhat.com>