Convert network API to use InfoCache object

This converts the db.info_cache_update() call in network/api to use
objects.  The save() method has been extended to support what we need
for cells.

Converting to the object allows us to ditch the conductor_api kwarg on
some methods.

Related to blueprint unified-object-model

Change-Id: I1722c03d20511d67acc0a8947de1d4273dc78597
Merge "Convert network API to use InfoCache object"