If the return was reached, then hostsPath would not be properly restored
to its original value. See the (lengthy) discussion at
https://golang.org/cl/15960047/

I assume that this is not for Go 1.2; mailing now since I promised to do so.
I will plan to ping once Go 1.2 is out.

R=rsc, bradfitz
CC=golang-dev
https://golang.org/cl/16200043