[SPARK-16299][SPARKR] Capture errors from R workers in daemon.R to avoid...

[SPARK-16299][SPARKR] Capture errors from R workers in daemon.R to avoid deletion of R session temporary directory.

## What changes were proposed in this pull request?
Capture errors from R workers in daemon.R to avoid deletion of R session temporary directory. See detailed description at https://issues.apache.org/jira/browse/SPARK-16299

## How was this patch tested?
SparkR unit tests.

Author: Sun Rui <sunrui2016@gmail.com>

Closes #13975 from sun-rui/SPARK-16299.

R/pkg/inst/worker/daemon.R

@@ -44,7 +44,7 @@ while (TRUE) {
     if (inherits(p, "masterProcess")) {
       close(inputCon)
       Sys.setenv(SPARKR_WORKER_PORT = port)
-      source(script)
+      try(source(script))
       # Set SIGUSR1 so that child can exit
       tools::pskill(Sys.getpid(), tools::SIGUSR1)
       parallel:::mcexit(0L)