make .noannex file prevent repo fixups

Avoid performing repository fixups for submodules and git-worktrees
when there's a .noannex file that will prevent git-annex from being
used in the repository.

This change is ok as long as the .noannex file is really going to prevent
git-annex from being used. But, init --force could override the file.
Which would result in the repo being initialized without the fixups
having run.

To avoid that situation decided to change init, to not let --force be used
to override a .noannex file. Instead the user can just delete the file.

doc/todo/Avoid_repo_fixup_if___34__.noannex__34___is_present.mdwn

@@ -39,3 +39,5 @@ Here's a demo of the issue:
     operating system: linux x86_64
     supported repository versions: 5 7
     upgrade supported from repository versions: 0 1 2 3 4 5 6
+
+> [[fixed|done]] --[[Joey]]