Bug tz and object series concatenation 
Related to #11755 ,#11693. Will be fixed in  #11705

``` python

In [1]: import pandas as pd

In [2]: x = pd.Series(pd.date_range('20151124 10:00', '20151124 11:00', freq = '1h', tz = "UTC") )

In [3]: y = pd.Series(['a','b'])

In [4]: print(pd.concat([x,y]))
```

AttributeError: 'numpy.ndarray' object has no attribute 'tz_localize'
