Consider grep return value 1 as success (#907)

* Allow Offline scanning on Alpine

* Consider grep return value 1 as success

scan/base.go

@@ -555,7 +555,7 @@ func (l *base) scanLibraries() (err error) {
 		// find / -name "*package-lock.json" -o -name "*yarn.lock" ... 2>&1 | grep -v "Permission denied"
 		cmd := fmt.Sprintf(`find / ` + findopt[:len(findopt)-3] + ` 2>&1 | grep -v "Permission denied"`)
 		r := exec(l.ServerInfo, cmd, noSudo)
-		if !r.isSuccess() {
+		if r.ExitStatus != 0 && r.ExitStatus != 1 {
 			return xerrors.Errorf("Failed to find lock files")
 		}
 		detectFiles = append(detectFiles, strings.Split(r.Stdout, "\n")...)