Fix cannot cast object 'false' to Integer

The predefined value of MaxRetries ist 0. Groovy interpret this as a
boolean false instead of an integer.

A call with 0 raised the following exception:

Cannot cast object 'false' with class 'java.lang.Boolean' to class
'java.lang.Integer'

The applied fix, catches a possible boolean value and transforms it to
an integer.

Author: eberhardtj

scripts/ParallelPost.groovy

@@ -86,7 +86,7 @@ inputStream.withReader(utf8, { reader ->
     writer.setBatchSize((Integer) options.b)
     writer.setCommitWithinMs((Integer) options.d)
     writer.setThreads((Integer) options.t)
-    writer.setMaxRetries((Integer) options.r)
+    writer.setMaxRetries(options.r ? options.r.toInteger() : 0)
     writer.setWaitMs((Integer) options.w)
 
     decoder.setReceiver(handler)