lfs: drop deprecated remote store config options
The last of these were removed from fb-experimental in
86884a51e9aa, and we
might as well clean this up before the freeze.
py3: use bytes instead of pycompat.bytestr
Follow up for
35fb3367f72d.
Differential Revision: https://phab.mercurial-scm.org/D1854
test-pull-r: explicitly kill server processes
Differential Revision: https://phab.mercurial-scm.org/D1855