tools/xc: restore logging in xc_save

tools/xc: restore logging in xc_save

Prior to xen-4.1 the helper xc_save would print some progress during
migration. With the new xc_interface_open API no more messages were
printed because no logger was configured.

Restore previous behaviour by providing a logger. The progress in
xc_domain_save will be disabled because it generates alot of output and
fills up xend.log quickly.

Signed-off-by: Olaf Hering <olaf@aepfle.de>
Acked-by: Ian Campbell <ian.campbell@citrix.com>
Committed-by: Ian Campbell <ian.campbell@citrix.com>