The P4 repository can erroneously consider a file to be "inside" a symlink to a
directory. 'p4 sync' (the client) reports an error if it encounters this
situation, but 'hg update' aborts.
Work around the problem by discarding such files. In the testcase, we can't
accept changelist #2, because we have no changelist that deletes the symlink,
so instead we have to ignore the new file.