Fix handle_opendir() in the sdcard daemon

The fuse_open_out structure returned to the kernel by handle_opendir()
was not properly initializing all the fields.  The symptom was recursive
ls (ls -R) failing on the emulated sdcard filesystem, because rewinddir(3)
was failing with ESPIPE.

Bug: 7168594
Change-Id: I56ddfd3453e6aac34fe6e001e88c4c46fb2eb271