BUG: Bug in setting with loc/ix a single indexer on a multi-index axis and a listlike (related to GH3777)

[jreback]

related to #3777

This shows enlarging (and setting inplace)

In [8]: df = DataFrame(np.random.randint(5,10,size=9).reshape(3, 3),
   ...:    ...:                        columns=list('abc'),
   ...:    ...:                        index=[[4,4,8],[8,10,12]])

In [9]: 

In [9]: df
Out[9]: 
      a  b  c
4 8   8  8  8
  10  9  7  6
8 12  8  7  9

In [10]: df.loc[4,'d'] = [0,1.]

In [11]: df
Out[11]: 
      a  b  c   d
4 8   8  8  8   0
  10  9  7  6   1
8 12  8  7  9 NaN

In [12]: df.loc[4,'d'] = [3,4]

In [13]: df
Out[13]: 
      a  b  c   d
4 8   8  8  8   3
  10  9  7  6   4
8 12  8  7  9 NaN

Invalid assignments

In [10]: df.loc[4,'d'] = [3]
ValueError: cannot set using a multi-index selection indexer with a different length than the value

In [11]: df.loc[4,'d'] = [3,4,5]
ValueError: cannot set using a multi-index selection indexer with a different length than the value