Add share_server_id filter option to 'get_all' share API method

Added one more filter option - 'share_server_id' to 'get_all' method,
by default only admin can list shares with it.
Also made little refactor for this method and covered with unittests.
Added tempest tests to cover changes.

Partially-implements blueprint add-admin-api-list-shares-for-share-server

Change-Id: I54f5458d3bb365c7a6fd0c8c7dce664cc7d01fc2
Merge "Add share_server_id filter option to 'get_all' share API method"