contrib: add sshfs-benchmark.bash

Let's get some reproducible numbers for
https://github.com/rfjakob/gocryptfs/issues/481
and
https://github.com/rfjakob/gocryptfs/issues/410

Example run:

$ ./sshfs-benchmark.bash nuetzlich.net
working directory: /tmp/sshfs-benchmark.bash.vu4
sshfs mounted: nuetzlich.net:/tmp -> sshfs.mnt
gocryptfs mounted: sshfs.mnt/sshfs-benchmark.bash.KM9/gocryptfs.crypt -> gocryptfs.mnt

                         sshfs  gocryptfs-on-sshfs
git init                  1.68               11.23
rsync                     6.07               20.35

0 files changed, 0 insertions, 0 deletions