[SPARK-17193][CORE] HadoopRDD NPE at DEBUG log level when getLocationInfo == null

## What changes were proposed in this pull request?

Handle null from Hadoop getLocationInfo directly instead of catching (and logging) exception

## How was this patch tested?

Jenkins tests

Author: Sean Owen <sowen@cloudera.com>

Closes #14760 from srowen/SPARK-17193.