Create default network for more compute tests

Chipping away at the referenced bug, this commit uses the
create_default_network class-level variable introduced via [1] to
trigger setup_credentials to create a default network for
a handful more test cases in which the problem was observed.

[1] Ia34fe3b41261de02918713c2a948e6c56554bf6f
Partial-Bug: #1844568

Change-Id: Ic38c74c245fddf29826e6ca0cc469f919076355e
4 files changed