[SPARK-14594][SPARKR] check execution return status code

[felixcheung]

What changes were proposed in this pull request?

When JVM backend fails without going proper error handling (eg. process crashed), the R error message could be ambiguous.

Error in if (returnStatus != 0) { : argument is of length zero

This change attempts to make it more clear (however, one would still need to investigate why JVM fails)

How was this patch tested?

manually

[SparkQA]

Test build #56741 has finished for PR 12622 at commit f5f46c5.

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

[shivaram]

LGTM. It'll be good to know more information though. Maybe we can add a log message for the JVM with an exit handler or something like that ?

[felixcheung]

JVM addShutdownHook is being added for a couple for things and they have logging, for example:

https://github.com/apache/spark/blob/master/core/src/main/scala/org/apache/spark/util/ShutdownHookManager.scala

spark/core/src/main/scala/org/apache/spark/SparkContext.scala

Line 559 in af1f4da

_shutdownHookRef = ShutdownHookManager.addShutdownHook(

But unfortunately they are not guaranteed to be called if the process is terminated abruptly.
If we are concerned I think we should get a specific repro step to check if we have logging for that case, if possible.

[shivaram]

Ok - this is good for now. I'll merge this PR and we can revisit this if we have a better repro.