[SPARK-17442][SPARKR] Additional arguments in write.df are not passed to data source

## What changes were proposed in this pull request?

additional options were not passed down in write.df.

## How was this patch tested?

unit tests
falaki shivaram

Author: Felix Cheung <felixcheung_m@hotmail.com>

Closes #15010 from felixcheung/testreadoptions.