Do not unmount /mnt/product/* when vold starts

Bug: 110808288
Test: Boot a device and checks /mnt/product/foo mounted in early mount
      isn't unmounted.

Change-Id: Ide411cd78565505bc72ed57e79f3d31b6392b27c

VolumeManager.cpp

@@ -754,7 +754,8 @@ int VolumeManager::unmountAll() {
     while ((mentry = getmntent(fp)) != NULL) {
         auto test = std::string(mentry->mnt_dir);
         if ((android::base::StartsWith(test, "/mnt/") &&
-             !android::base::StartsWith(test, "/mnt/vendor")) ||
+             !android::base::StartsWith(test, "/mnt/vendor") &&
+             !android::base::StartsWith(test, "/mnt/product")) ||
             android::base::StartsWith(test, "/storage/")) {
             toUnmount.push_front(test);
         }