migration/block: reset dirty bitmap before read in bulk phase

migration/block: reset dirty bitmap before read in bulk phase

Reset the dirty bitmap before reading to make sure we don't miss
any new data.

Cc: qemu-stable@nongnu.org
Signed-off-by: Peter Lieven <pl@kamp.de>
Message-Id: <1520507908-16743-3-git-send-email-pl@kamp.de>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
(cherry picked from commit 86b124bc76bd7137d0fb20696c4e349571b8533d)
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>