Bug 4295: Fixed incorrectly introduced nodes when MERGE was followed by DELETE

ModificationNode lost state in situations when
parent node was MERGE which indroduced child nodes
and child node was deleted. That resulted into recording NONE,
which during apply of MERGE was expanded back to original MERGE
which caused reintroduction of deleted node.

Change-Id: Ia2085f5475b49957ef8ac7ab6c629ca3eef803f2
Signed-off-by: Tony Tkacik <ttkacik@cisco.com>