Fix rebase for init error

Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@crosbymichael.com> (github: crosbymichael)
Upstream-commit: d5112ffce60625e470515578ccd446a191dd9e88
Component: engine

components/engine/execdriver/lxc/driver.go

@@ -43,7 +43,7 @@ func init() {
 			os.Exit(127)
 		}
 		if err := syscall.Exec(path, args.Args, os.Environ()); err != nil {
-			panic(err)
+			return fmt.Errorf("dockerinit unable to execute %s - %s", path, err)
 		}
 		panic("Unreachable")
 	})