Test suite located in module
contrib/tempest/tempest/api/share/admin/test_multi_backend.py
creates 2 shares without waiting for "available" status and then waits for
status. In this case "retry" functionality is not used.
Add method 'create_shares' to base class that does parallel share
creation with recreation as it is done with single request. And use this
method in mentioned test module.
Change-Id: I1314c9494a547314cd9bb9b03323470d58956fac
Closes-Bug: #1406770
a52d1b49a6