[SPARK-19399][SPARKR][BACKPORT-2.1] fix tests broken by merge

[felixcheung]

What changes were proposed in this pull request?

fix test broken by git merge for #16739

How was this patch tested?

manual

[SparkQA]

Test build #72980 has finished for PR 16950 at commit 6fad435.

• This patch fails R style tests.
• This patch merges cleanly.
• This patch adds no public classes.

[SparkQA]

Test build #72981 has finished for PR 16950 at commit c685507.

• This patch fails SparkR unit tests.
• This patch merges cleanly.
• This patch adds no public classes.

[SparkQA]

Test build #72982 has finished for PR 16950 at commit 2b98d74.

• This patch passes all tests.
• This patch merges cleanly.
• This patch adds no public classes.

[felixcheung]

merged to branch-2.1