autotest: Pick WiFi interfaces for WiFiClient by asking shill

Test code wants to reason about the WiFi interface that shill
is controlling.  To do this, just ask shill which interface
it is controlling rather than duplicating shill's heuristics
for picking interfaces.

While here, remove some deprecated fields that are no longer used.

TEST=Tests now pass when the interface managed by shill is an
IBSS interface rather than a managed interface.

Change-Id: If00db60b517bf124d6edd05b57f74a29065ecb3c
(cherry picked from commit ba5df3ecf6c5cda20439633bb19aac4f33d835db)
Tested-by: Christopher Wiley <>
Reviewed-by: Paul Stewart <>
Commit-Queue: Christopher Wiley <>
2 files changed