my_init: runsvdir no longer redirects stderr to proctitle.

As described at http://smarden.org/runit/runsvdir.8.html passing a log
option to runsvdir causes stderr to be redirected to the proctitle.

That prevents stderr from reaching docker logs, which is a big problem.
Merge pull request #94 from pda/stderr-not-proctitle

my_init: runsvdir no longer redirects stderr to proctitle.