[SPARK-2888] [SQL] Fix addColumnMetadataToConf in HiveTableScan

JIRA: https://issues.apache.org/jira/browse/SPARK-2888

Author: Yin Huai <huai@cse.ohio-state.edu>

Closes #1817 from yhuai/fixAddColumnMetadataToConf and squashes the following commits:

fba728c [Yin Huai] Fix addColumnMetadataToConf.