hosts: Unset HOSTS_PATH from the environment

goodhosts unconditionnally uses this environment variable as an override
for the hosts file to use. We don't want admin-helper to modify
arbitrary file, so we have to unset it before calling into goodhosts.

pkg/hosts/hosts.go

@@ -2,6 +2,7 @@ package hosts
 
 import (
 	"fmt"
+	"os"
 	"regexp"
 	"runtime"
 	"sort"
@@ -27,6 +28,14 @@ type Hosts struct {
 	HostFilter func(string) bool
 }
 
+func init() {
+	// goodhosts unconditionnally uses this environment variable
+	// as an override for the hosts file to use. We don't want admin-helper
+	// to modify arbitrary file, so we have to unset it before calling into
+	// goodhosts.
+	os.Unsetenv("HOSTS_PATH")
+}
+
 func New() (*Hosts, error) {
 	file, err := hostsfile.NewHosts()
 	if err != nil {