Warning while reindexing tz aware index with method='nearest'
Reindexing a tz aware dataframe using method='nearest' raise an internal warning.
```python
from pandas.util.testing import makeTimeDataFrame
df = makeTimeDataFrame(freq='1h')
df = df.tz_localize('UTC')
df.reindex(df.index[1:4], method='nearest')
```
raises a warning:
```
/lib/python3.7/site-packages/pandas/core/indexes/base.py:2820: FutureWarning: Converting timezone-aware DatetimeArray to timezone-naive ndarray with 'datetime64[ns]' dtype. In the future, this will return an ndarray with 'object' dtype where each element is a 'pandas.Timestamp' with the correct 'tz'.
        To accept the future behavior, pass 'dtype=object'.
        To keep the old behavior, pass 'dtype="datetime64[ns]"'.
  target = np.asarray(target)
```
in pandas 0.24.2