since kdump may getprotobynumber() late, do not drop "rpath". We could

since kdump may getprotobynumber() late, do not drop "rpath".  We could
potentially modify pledge() to permit /etc/protocols (/etc/rpc?
/etc/services? etc) without requiring a rpath attribute.. but where would
we draw the line for what /etc files libc functions need?  At present, we
draw that line closer to the minimum.
issue found by theo@math.ethz.ch