vold: Support aborting FUSE connections.

This can be done through binder as well as vdc, using 'vdc volume
abort_fuse'.

Bug: 153411204
Test: adb shell vdc volume abort_fuse
Change-Id: I93e46dc1cd361729cc1162c63520cf73152ea409
diff --git a/VolumeManager.h b/VolumeManager.h
index a9087fd..3277f75 100644
--- a/VolumeManager.h
+++ b/VolumeManager.h
@@ -120,6 +120,8 @@
     int remountUid(uid_t uid, int32_t remountMode);
     int remountAppStorageDirs(int uid, int pid, const std::vector<std::string>& packageNames);
 
+    /* Aborts all FUSE filesystems, in case the FUSE daemon is no longer up. */
+    int abortFuse();
     /* Reset all internal state, typically during framework boot */
     int reset();
     /* Prepare for device shutdown, safely unmounting all devices */