SONAR suggestion - log exceptions, don't print stack traces

Change-Id: I4814a0662912706df005972d44c48a7db39ecd50
diff --git a/apps/dhcprelay/src/main/java/org/onosproject/dhcprelay/Dhcp6HandlerImpl.java b/apps/dhcprelay/src/main/java/org/onosproject/dhcprelay/Dhcp6HandlerImpl.java
index 0cb3468..09a118c 100644
--- a/apps/dhcprelay/src/main/java/org/onosproject/dhcprelay/Dhcp6HandlerImpl.java
+++ b/apps/dhcprelay/src/main/java/org/onosproject/dhcprelay/Dhcp6HandlerImpl.java
@@ -648,7 +648,7 @@
                 recordSemaphore.release();
             }
         } catch (InterruptedException e) {
-            e.printStackTrace();
+            Thread.currentThread().interrupt();
         }
     }
 
@@ -807,7 +807,7 @@
                 recordSemaphore.release();
             }
         } catch (InterruptedException e) {
-            e.printStackTrace();
+            Thread.currentThread().interrupt();
         }
     }