migration: recognize COLO as part of activating process

migration: recognize COLO as part of activating process

We will migrate parts of dirty pages backgroud lively during the gap time
of two checkpoints, without this modification, it will not work
because ram_save_iterate() will check it before send RAM_SAVE_FLAG_EOS
at the end of it.

Signed-off-by: zhanghailiang <zhang.zhanghailiang@huawei.com>
Message-Id: <20200224065414.36524-7-zhang.zhanghailiang@huawei.com>
Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>