qemu.tests: Add live_snapshot case

1. create live snapshot during file creating
2. create live snapshot when guest reboot

Signed-off-by: Suqin Huang <shuang@redhat.com>
Acked-by: Qingtang Zhou <qzhou@redhat.com>
Acked-by: Feng Yang <fyang@redhat.com>
qemu.tests: Add live_snapshot with file transfer

create live snapshot during file transfer

Signed-off-by: Suqin Huang <shuang@redhat.com>
Acked-by: Qingtang Zhou <qzhou@redhat.com>
Acked-by: Feng Yang<fyang@redhat.com>
qemu.tests: live_snapshot update

Update the functions using in this scripts to date and bug fix

Signed-off-by: Suqing Huang <shuang@redhat.com>
Signed-off-by: Feng Yang <fyang@redhat.com>
Signed-off-by: Qingtang Zhou <qzhou@redhat.com>
Signed-off-by: Yiqiao Pu <ypu@redhat.com>
qemu.tests: add base test for livesnapshot

This script check file content not changes after create livesnapshot;
changes from v1:
    1). used utils.has_file instead get md5 by shell command
    2). instead guest_name param with os_type param to identify guest
    os type

small fix, instead guest_name param with os_type param

Signed-off-by: Xu Tian <xutian@redhat.com>
Acked-by: Feng Yang <fyang@redhat.com>
qemu.tests: Add live snapshot chain cases

Add five live snapshot cases have similar process:
- create live snapshot when guest paused
- restore to previous state when guest become crash
- restore live snapshot after guest update
- restore live snapshot chain 2-restore to base
- restore to parent snapshot node

Signed-off-by: Yiqiao Pu <ypu@redhat.com>

Update interface to date

Signed-off-by: Yiqiao Pu <ypu@redhat.com>
Signed-off-by: Feng Yang <fyang@redhat.com>