Revert "check whether the network interface exists before using it"

This reverts commit a5faa56a.

Reason for revert: <Potential culprit for b/379818258  - verifying through ABTD before revert submission. This is part of the standard investigation process, and does not mean your CL will be reverted.>

Change-Id: Ib41a4bf760fd98e9fbc469a20af5bc3ed97e0cee