## What changes were proposed in this pull request?

A fix to https://issues.apache.org/jira/browse/SPARK-21727, "Operating on an ArrayType in a SparkR DataFrame throws error"

## How was this patch tested?

- Ran tests at R\pkg\tests\run-all.R (see below attached results)
- Tested the following lines in SparkR, which now seem to execute without error:

```
indices <- 1:4
myDf <- data.frame(indices)
myDf$data <- list(rep(0, 20))
mySparkDf <- as.DataFrame(myDf)
collect(mySparkDf)
```

[2018-01-22 SPARK-21727 Test Results.txt](https://github.com/apache/spark/files/1653535/2018-01-22.SPARK-21727.Test.Results.txt)

felixcheung yanboliang sun-rui shivaram

_The contribution is my original work and I license the work to the project under the project’s open source license_

Author: neilalex <neil@neilalex.com>

Closes #20352 from neilalex/neilalex-sparkr-arraytype.