Specifies the appropriate ip address in case of multi-networking

When connecting a storage_network to VMs, the tests may try
to associate a FloatingIP to the storage network instead of the
project network.

Note: This failure has been caused since [1] was merged

[1] https://review.opendev.org/#/c/668597/

Change-Id: Ife32cb2616701a285cb16d5b267bdf6a78d74c3c
2 files changed