MFC r298462:

Return ret in op_ifentry(..) to mute a -Wunused-but-set-variable warning

This will also now detect error conditions with
value->var.subs[sub - 1] == LEAF_ifPhysAddress where string_get(..)
could fail if iifp->physaddr and/or iifp->physaddrlen were deemed
invalid.

CID: 1006551