Commit

	17c7e2cd loopback: show original directory in "df"

added the FsName field to MountOptions, but looks like

	d31db957 fuse: allow setting the fsname (first column in df -T)

forgot that it exists. Use it now.

This will be important for DirectMount, as passing "fsname=xxx" to
the mount syscall causes the kernel to reject with EINVAL and this
message in dmesg:

	[132274.900267] fuse: Unknown parameter 'fsname'

Change-Id: Ic1233fe9306e2ce05f85189eecceecec2baa44b7