cmdutil: fix an uninitialize variable usage in clearunfinished()

I happened to notice that PyCharm flagged this while looking for something else.
I'm pretty sure it meant to check the current state in the iteration, and not
keep reusing the last one in the previous iteration.

Differential Revision: https://phab.mercurial-scm.org/D10459

mercurial/cmdutil.py

@@ -3776,7 +3776,7 b' def clearunfinished(repo):'
             raise error.StateError(state.msg(), hint=state.hint())
 
     for s in statemod._unfinishedstates:
-        if s._opname == b'merge' or state._reportonly:
+        if s._opname == b'merge' or s._reportonly:
             continue
         if s._clearable and s.isunfinished(repo):
             util.unlink(repo.vfs.join(s._fname))