syscall: allow nacl's fake network code to Listen twice on the same address
Noticed from nacl trybot failures on new tests in
https://golang.org/cl/16630
Related earlier fix of mine to nacl's listen code:
syscall: fix nacl listener to not accept connections once closed
https://go-review.googlesource.com/15940
Perhaps a better fix (in the future?) would be to remove the listener
from the map at close, but that didn't seem entirely straightforward
last time I looked into it. It's not my code, but it seems that the
map entry continues to have a purpose even after Listener close. (?)
But given that this code is only really used for running tests and the
playground, this seems fine.
Change-Id: I43bfedc57c07f215f4d79c18f588d3650687a48f
Reviewed-on: https://go-review.googlesource.com/16650
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org> Reviewed-by: Ian Lance Taylor <iant@golang.org>