Add ability to pass share network by name in manilaclient

Add ability to pass share network by name when doing

- share-network-show
- share-network-update
- share-network-delete

Add 'update' and 'delete' methods to ShareNetwork class.

Closes-Bug: #1324919

Change-Id: If81ecd35e13d03329d6c15c57a4d149ded13ec8e