Remove sandbox specific bind mounts from root namespace.

Update vold to only create package sandboxes and not do any bind mounts.
After zygote forks, all the necessary bind mounts will be setup for
the process.

Bug: 124009234
Test: manual
Test: atest cts/hostsidetests/appsecurity/src/android/appsecurity/cts/ExternalStorageHostTest.java
Test: atest DownloadProviderTests
Test: atest cts/tests/app/src/android/app/cts/DownloadManagerTest.java
Test: atest MediaProviderTests
Test: atest cts/tests/tests/provider/src/android/provider/cts/MediaStore*

Change-Id: Ia42209cb74cbc423bb09c1c51cb7a164f7c568da
diff --git a/Utils.h b/Utils.h
index e51ec1e..574bcd4 100644
--- a/Utils.h
+++ b/Utils.h
@@ -57,6 +57,12 @@
 /* Creates bind mount from source to target */
 status_t BindMount(const std::string& source, const std::string& target);
 
+/** Creates a symbolic link to target */
+status_t Symlink(const std::string& target, const std::string& linkpath);
+
+/** Calls unlink(2) at linkpath */
+status_t Unlink(const std::string& linkpath);
+
 bool FindValue(const std::string& raw, const std::string& key, std::string* value);
 
 /* Reads filesystem metadata from device at path */