Merge pull request #933 from xutian/migration

qemu.migration: disable automem to avoid migration failed

qemu/tests/cfg/migrate.cfg

 - migrate: install setup image_copy unattended_install.cdrom
     type = migration
+    automem = no
     migration_test_command = help
     migration_bg_command = "cd /tmp; nohup tcpdump -q -i any -t ip host localhost"
     migration_bg_check_command = pgrep tcpdump