BUG-4359: use WRITE-implied metadata

BUG-4359: use WRITE-implied metadata

When we apply an operation under a WRITE node, we need to look up the
metadata based on that write to correctly understand what the effect of
this operation is.

This is important when we modify data introduced by the WRITE node, as
without this lookup a WRITE/DELETE combination on the child will result
in a NONE logical operation, which means data introduced in the WRITE
node will not be modified and seemingly reappear.

Change-Id: I5a5a67470f1f8baafc7a71069341dead073ba84a
Signed-off-by: Robert Varga <rovarga@cisco.com>