[NO ISSUE][RT] Fix getting file descriptor counters

- user model changes: no
- storage format changes: no
- interface changes: no

Details:
- The OS Bean methods return Longs. Prior to this change, there
  was a cast to Integer which always throws a ClassCastException.

Change-Id: Ia6c7cdd26475075975e5850d9fe19b3063d5d9f6
Reviewed-on: https://asterix-gerrit.ics.uci.edu/2607
Sonar-Qube: Jenkins <jenkins@fulliautomatix.ics.uci.edu>
Tested-by: Jenkins <jenkins@fulliautomatix.ics.uci.edu>
Contrib: Jenkins <jenkins@fulliautomatix.ics.uci.edu>
Integration-Tests: Jenkins <jenkins@fulliautomatix.ics.uci.edu>
Reviewed-by: Murtadha Hubail <mhubail@apache.org>
diff --git a/hyracks-fullstack/hyracks/hyracks-util/src/main/java/org/apache/hyracks/util/MXHelper.java b/hyracks-fullstack/hyracks/hyracks-util/src/main/java/org/apache/hyracks/util/MXHelper.java
index 2b65106..2545c25 100644
--- a/hyracks-fullstack/hyracks/hyracks-util/src/main/java/org/apache/hyracks/util/MXHelper.java
+++ b/hyracks-fullstack/hyracks/hyracks-util/src/main/java/org/apache/hyracks/util/MXHelper.java
@@ -64,27 +64,27 @@
         return getOpenFileDescriptorCount != null;
     }
 
-    public static Integer getCurrentOpenFileCount() {
+    public static Long getCurrentOpenFileCount() {
         if (getOpenFileDescriptorCount == null) {
-            return -1;
+            return -1L;
         }
         try {
-            return (Integer) getOpenFileDescriptorCount.invoke(osMXBean);
+            return (Long) getOpenFileDescriptorCount.invoke(osMXBean);
         } catch (Throwable e) { // NOSONAR
             LOGGER.log(Level.WARN, "Failure invoking getOpenFileDescriptorCount", e);
-            return -1;
+            return -1L;
         }
     }
 
-    public static Integer getMaxOpenFileCount() {
+    public static Long getMaxOpenFileCount() {
         if (getMaxFileDescriptorCount == null) {
-            return -1;
+            return -1L;
         }
         try {
-            return (Integer) getMaxFileDescriptorCount.invoke(osMXBean);
+            return (Long) getMaxFileDescriptorCount.invoke(osMXBean);
         } catch (Throwable e) { // NOSONAR
             LOGGER.log(Level.WARN, "Failure invoking getMaxFileDescriptorCount", e);
-            return -1;
+            return -1L;
         }
     }