Bug 2158: Fixed TopologyManager for edge updates.

MD-SAL does not keep the order of notification of data changes. In the
result, TopologyManager sometimes receives a notification of an edge
addition before it is notified of the addition of the NodeConnector
which is the head of the edge. In such a case, TopologyManager ignores
the edge notification, and fails to create correct topology information.
This is one of the root causes of Bug 2158.
To handle this issue, this patch fixed TopologyManager to queue edge
notifications, and wait corresponding NodeConnector updates.

Change-Id: Ifeabc91d856eb9cc88ae3595d14e0a6819ec7454
Signed-off-by: Hideyuki Tai <Hideyuki.Tai@necam.com>