qemu.tests: disable lsi device on Host_RHEL6.5 and Host_RHEL7.0

since lsi device is not support by RHEL6.5 and RHEL.7.0 host, so disable
it; And disable virtio-scsi on WinXP guest because it not support too;

Signed-off-by: Xu Tian <xutian@redhat.com>
virttest: fix save_to_file time when use qmp monitor

when QMP monitor used, migrate complete check always failed until
timeout; This commit update check method and raise QemuMigrationTimeout
expection when migrate timeout;

Signed-off-by: Xu Tian <xutian@redhat.com>