Fix creation of share without share-network

We get python error trying create share without specified share-network.
Also added unittests to cover "create" function and call of external
functions in it.

Change-Id: I6a504b72b1d6f7b8d442bd8f4d0791bbc10f1cd8
Closes-Bug: #1331076
Merge "Fix creation of share without share-network"