migration/block: reset dirty bitmap before reading

Any data that is returned by read may be stale already, the bitmap
has to be cleared before issuing the read.

Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <20170605123908.18777-16-pbonzini@redhat.com>
Signed-off-by: Fam Zheng <famz@redhat.com>
1 file changed