qemu-server: add support for unsecure migration (setting in datacenter.cfg)

qemu-server: add support for unsecure migration (setting in datacenter.cfg)

This patch adds support for unsecure migration using a direct tcp connection
KVM <=> KVM instead of an extra SSH tunnel. Without ssh the limit is just the
bandwith and no longer the CPU / one single core.

You can enable this by adding:
migration_unsecure: 1
to datacenter.cfg

Examples using qemu 1.4 as migration with qemu 1.3 still does not work for me:

current default with SSH Tunnel VM uses 2GB mem:
Dec 27 21:10:32 starting migration of VM 105 to node 'cloud1-1202' (10.255.0.20)
Dec 27 21:10:32 copying disk images
Dec 27 21:10:32 starting VM 105 on remote node 'cloud1-1202'
Dec 27 21:10:35 starting ssh migration tunnel
Dec 27 21:10:36 starting online/live migration on localhost:60000
Dec 27 21:10:36 migrate_set_speed: 8589934592
Dec 27 21:10:36 migrate_set_downtime: 1
Dec 27 21:10:38 migration status: active (transferred 152481002, remaining 1938546688), total 2156396544) , expected downtime 0
Dec 27 21:10:40 migration status: active (transferred 279836995, remaining 1811140608), total 2156396544) , expected downtime 0
Dec 27 21:10:42 migration status: active (transferred 421265271, remaining 1669840896), total 2156396544) , expected downtime 0
Dec 27 21:10:44 migration status: active (transferred 570987974, remaining 1520152576), total 2156396544) , expected downtime 0
Dec 27 21:10:46 migration status: active (transferred 721469404, remaining 1369939968), total 2156396544) , expected downtime 0
Dec 27 21:10:48 migration status: active (transferred 875595258, remaining 1216057344), total 2156396544) , expected downtime 0
Dec 27 21:10:50 migration status: active (transferred 1034654822, remaining 1056931840), total 2156396544) , expected downtime 0
Dec 27 21:10:54 migration status: active (transferred 1176288424, remaining 915369984), total 2156396544) , expected downtime 0
Dec 27 21:10:56 migration status: active (transferred 1339734759, remaining 752050176), total 2156396544) , expected downtime 0
Dec 27 21:10:58 migration status: active (transferred 1503743261, remaining 588206080), total 2156396544) , expected downtime 0
Dec 27 21:11:02 migration status: active (transferred 1645097827, remaining 446906368), total 2156396544) , expected downtime 0
Dec 27 21:11:04 migration status: active (transferred 1810562934, remaining 281751552), total 2156396544) , expected downtime 0
Dec 27 21:11:06 migration status: active (transferred 1964377505, remaining 126033920), total 2156396544) , expected downtime 0
Dec 27 21:11:08 migration status: active (transferred 2077930417, remaining 0), total 2156396544) , expected downtime 0
Dec 27 21:11:09 migration speed: 62.06 MB/s - downtime 37 ms
Dec 27 21:11:09 migration status: completed
Dec 27 21:11:13 migration finished successfuly (duration 00:00:41)
TASK OK

with unsecure migration without SSH Tunnel:
Dec 27 22:43:14 starting migration of VM 105 to node 'cloud1-1203' (10.255.0.22)
Dec 27 22:43:14 copying disk images
Dec 27 22:43:14 starting VM 105 on remote node 'cloud1-1203'
Dec 27 22:43:17 starting online/live migration on 10.255.0.22:60000
Dec 27 22:43:17 migrate_set_speed: 8589934592
Dec 27 22:43:17 migrate_set_downtime: 1
Dec 27 22:43:19 migration speed: 1024.00 MB/s - downtime 1100 ms
Dec 27 22:43:19 migration status: completed
Dec 27 22:43:22 migration finished successfuly (duration 00:00:09)
TASK OK