Add mount callback

Mounting a FUSE path needs two steps:
1. Mounting the filesystem
2. Starting the FUSE session in the FUSE daemon

The second part requires retriving an fd from (1) and the mount paths
and passing it to the FUSE daemon.

Previously, we'd return from the Vold mount call and mark the volume
as mounted while we scramble to do (2). This means there's a time
period where the Volume is marked as MOUNTED but not actually ready
and any IO access on the paths will hang forever. This could also be
misleading when interpreting bug reports.

Now, we block the Vold mount call until the FUSE session is started

Test: atest AdoptableHostTest
Bug: 144275217

Change-Id: I45238a31df71286f67ef1c65c711d0085d72e97f
diff --git a/binder/android/os/IVold.aidl b/binder/android/os/IVold.aidl
index 91c0172..8412f9a 100644
--- a/binder/android/os/IVold.aidl
+++ b/binder/android/os/IVold.aidl
@@ -17,6 +17,7 @@
 package android.os;
 
 import android.os.IVoldListener;
+import android.os.IVoldMountCallback;
 import android.os.IVoldTaskListener;
 
 /** {@hide} */
@@ -40,7 +41,8 @@
     void partition(@utf8InCpp String diskId, int partitionType, int ratio);
     void forgetPartition(@utf8InCpp String partGuid, @utf8InCpp String fsUuid);
 
-    FileDescriptor mount(@utf8InCpp String volId, int mountFlags, int mountUserId);
+    void mount(@utf8InCpp String volId, int mountFlags, int mountUserId,
+         IVoldMountCallback callback);
     void unmount(@utf8InCpp String volId);
     void format(@utf8InCpp String volId, @utf8InCpp String fsType);
     void benchmark(@utf8InCpp String volId, IVoldTaskListener listener);