Revert "Fix NetworkInterface cannot discover down links"

Abandoning this change for now, and restore back to luni-like sysfs
implementation instead to prevent breakage in N. Will reattempt the
change again in the future.

This reverts commit 70da41603ee0dc5ab547c778003b3ed03ce3e6a1.

Change-Id: I33355b2435b9a606e0284a7626326d7b68e9253b
1 file changed