### Please describe the problem.

When adding files to the annex and then deciding against it in an "unusual" way, git-annex gets confused and the file left behind can't be removed from the annex...

### What steps will reproduce the problem?

1. Add file with "git annex add"
2. Decide you don't need the file add all
3. "git rm -f newfile"
4. "git annex unused"
5. "git annex dropunused all"

### What version of git-annex are you using? On what operating system?

git-annex version: 5.20140210 on Debian unstable

### Please provide any additional information below.

[[!format sh """
# If you can, paste a complete transcript of the problem occurring here.
# If the problem is with the git-annex assistant, paste in .git/annex/daemon.log
$ git init
Initialized empty Git repository in /tmp/foo/.git/
$ ls -l
total 0
$ cp ~/download/hub-ctrl.c .
$ git add hub-ctrl.c
$ git commit
[master (root-commit) ed7eb68] A file.
 1 file changed, 412 insertions(+)
 create mode 100644 hub-ctrl.c
$ cp ~/download/hub-ctrl .
$ ls -l
total 28
-rwxr-xr-x 1 tobias tobias 14130 Feb 19 00:49 hub-ctrl
-rw-r--r-- 1 tobias tobias  9270 Feb 19 00:48 hub-ctrl.c
$ git annex init
init  ok
(Recording state in git...)
$ git annex add
add hub-ctrl ok
(Recording state in git...)
$ git status
On branch master
Changes to be committed:
  (use "git reset HEAD <file>..." to unstage)

	new file:   hub-ctrl

$ git rm hub-ctrl
error: the following file has changes staged in the index:
    hub-ctrl
(use --cached to keep the file, or -f to force removal)
$ git rm -f hub-ctrl
rm 'hub-ctrl'
$ git status
On branch master
nothing to commit, working directory clean
$ git annex unused
unused . (checking for unused data...) (checking HEAD...) 
  Some annexed data is no longer used by any files:
    NUMBER  KEY
    1       SHA256E-s14130--d4e777ba2b99ed0a520fbabe7b93cf2165373b4945afe8dcb626231d9051f19d
  (To see where data was previously used, try: git log --stat -S'KEY')
  
  To remove unwanted data: git-annex dropunused NUMBER
  
ok
$ git annex dropunused all
dropunused 1 (unsafe) 
  Could only verify the existence of 0 out of 1 necessary copies

  Rather than dropping this file, try using: git annex move

  (Use --force to override this check, or adjust numcopies.)
failed
git-annex: dropunused: 1 failed
$

# End of transcript or log.
"""]]

> It seems to me that if you run `git annex dropunused --force`, it will
> remove the file. This needing --force is a recent change; git-annex
> tries to never posibly lose data unless forced. Dropping the last
> copy of a file certianly qualifies. [[done]] --[[Joey]]
