tests/test-remotefilelog-share.t

run-tests: fix `HGTESTEXTRAEXTENSIONS` with py3

Since `extensions` was a str and `section` bytes, it never populated anything.
If it had, it would have put bytes into the environment dictionary that is all
str.  As everything starts and ends as str, remove the incomplete attempt at
byteification.  It doesn't appear that we had any test coverage of this bit of
code, so also add a non-extension config to make sure it is filtered out
properly.

Differential Revision: https://phab.mercurial-scm.org/D9557

#require no-windows

#testcases safe normal

#if safe
  $ echo "[format]"         >> $HGRCPATH
  $ echo "exp-share-safe = True" >> $HGRCPATH
#endif

  $ . "$TESTDIR/remotefilelog-library.sh"

  $ cat >> $HGRCPATH <<EOF
  > [extensions]
  > remotefilelog=
  > share=
  > EOF

  $ hg init master
  $ cd master
  $ cat >> .hg/hgrc <<EOF
  > [remotefilelog]
  > server=True
  > EOF
  $ echo x > x
  $ hg commit -qAm x

  $ cd ..


  $ hgcloneshallow ssh://user@dummy/master source --noupdate -q
  $ hg share source dest
  updating working directory
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ hg -R dest unshare