The translation of the auth arg handling workarounds from OSC missed
a detail in the differences between OSC's option Namespace and
os-client-config's config dict: the auth args are in a 'auth' sub-dict.
Also expanded some of the testing to catch more edge cases.
Closes-Bug: 1603479
Change-Id: I80bb42992a1a93857be4c6367405df645780a33d