Migrate auth process to using the lookback IP address flow

Update Acloud auth process from deplicated OOB flow to lookback IP address
flow for desktop clients.

Bug: 243715425
Test: rm ~/.acloud_oauth2.dat; acloud-dev create
Change-Id: Icbc3300f21bc7b5de0f2a629fcd976b0d76d31a1
1 file changed