Marios Titas running a Haskell program noticed a problem with fuse's
readdirplus: when it is interrupted by a signal, it skips one directory
entry.

The reason is that fuse erronously updates ctx->pos after a failed
dir_emit().

The issue originates from the patch adding readdirplus support.
Reported-by: NJakob Unterwurzacher <jakobunt@gmail.com>
Tested-by: Marios Titas <redneb@gmx.com> 
Signed-off-by: NMiklos Szeredi <mszeredi@redhat.com>
Fixes: 0b05b183 ("fuse: implement NFS-like readdirplus support")
Cc: <stable@vger.kernel.org> # v3.9