Fix build on Solaris

internal/upgrade/upgrade_common.go

@@ -9,8 +9,6 @@ import (
 	"errors"
 	"strconv"
 	"strings"
-
-	"bitbucket.org/kardianos/osext"
 )
 
 type Release struct {
@@ -40,12 +38,7 @@ func init() {
 func UpgradeTo(rel Release, archExtra string) error {
 	select {
 	case <-upgradeUnlocked:
-		path, err := osext.Executable()
-		if err != nil {
-			upgradeUnlocked <- true
-			return err
-		}
-		err = upgradeTo(path, rel, archExtra)
+		err := upgradeTo(rel, archExtra)
 		// If we've failed to upgrade, unlock so that another attempt could be made
 		if err != nil {
 			upgradeUnlocked <- true