Fix Windows named pipes with Java security manager (elastic/elasticsearch#410)

The problem is that the Java security manager can open the pipe and then
quickly close it, leading to a need to reconnect from the C++ side.

Original commit: elastic/x-pack-elasticsearch@772b57f443

elasticsearch/src/main/java/org/elasticsearch/xpack/prelert/job/logging/CppLogMessageHandler.java

@@ -153,7 +153,10 @@ public class CppLogMessageHandler implements Closeable {
                 // No more markers in this block
                 break;
             }
-            parseMessage(xContent, bytesRef.slice(from, nextMarker - from));
+            // Ignore blank lines
+            if (nextMarker > from) {
+                parseMessage(xContent, bytesRef.slice(from, nextMarker - from));
+            }
             from = nextMarker + 1;
         }
         return bytesRef.slice(from, bytesRef.length() - from);

elasticsearch/src/main/java/org/elasticsearch/xpack/prelert/job/manager/AutodetectProcessManager.java

@@ -112,8 +112,10 @@ public class AutodetectProcessManager extends AbstractComponent implements DataP
             if (e.getCause() instanceof TimeoutException) {
                 logger.warn("Connection to process was dropped due to a timeout - if you are feeding this job from a connector it " +
                         "may be that your connector stalled for too long", e.getCause());
+            } else {
+                logger.error("Unexpected exception", e);
             }
-            throw ExceptionsHelper.serverError(msg);
+            throw ExceptionsHelper.serverError(msg, e);
         }
     }