crypto/tls: add FreeBSD root certificate location

    Fixes #2721.

R=golang-dev, bradfitz
CC=golang-dev
https://golang.org/cl/5532090

src/pkg/crypto/tls/root_unix.go

@@ -13,10 +13,11 @@ import (
 
 // Possible certificate files; stop after finding one.
 var certFiles = []string{
-	"/etc/ssl/certs/ca-certificates.crt", // Linux etc
-	"/etc/pki/tls/certs/ca-bundle.crt",   // Fedora/RHEL
-	"/etc/ssl/ca-bundle.pem",             // OpenSUSE
-	"/etc/ssl/cert.pem",                  // OpenBSD
+	"/etc/ssl/certs/ca-certificates.crt",     // Linux etc
+	"/etc/pki/tls/certs/ca-bundle.crt",       // Fedora/RHEL
+	"/etc/ssl/ca-bundle.pem",                 // OpenSUSE
+	"/etc/ssl/cert.pem",                      // OpenBSD
+	"/usr/local/share/certs/ca-root-nss.crt", // FreeBSD
 }
 
 func initDefaultRoots() {