[Python] Dataset segfault when not importing pyarrow.parquet

To reproduce:

1. import pyarrow.parquet # if we skip this...
   import pyarrow as pa
   import pyarrow.dataset as ds
   import glob
   ds = pa.dataset.dataset('/data/taxi_parquet/data_0.parquet')
   ds.to_table() # this will crash
    
   $ python pyarrow/crash.py dev
   terminate called after throwing an instance of 'parquet::ParquetException'
   what(): The file only has 19 columns, requested metadata for column: 1049198736
   [1] 1559395 abort (core dumped) python pyarrow/crash.py
    
   When the import is there, it will work fine.