Put back some deleted code.

http://ag/507249 removed a bunch of supposedly dead (unused) code. It turns out
at least ifc_disable() is being used in some protected partner branches. Put
back that as well as ifc_enable() to keep it symmetric.

Bug: 15413389
Change-Id: Ibec83a66e5d9079876ccf36d250b95b7c0294c03