Update share_network obj after db update

With first usage of share-network, backend driver receives share_network
without 'cidr' value for subnet, because obj was gotten before db update
with 'cidr' value. So we add additional re-get in case network-allocations
stuff used.

Change-Id: Id3ae1cbde96c583423943ad72f4879b1a71e942a
Closes-Bug: #1358707
Merge "Update share_network obj after db update"