Catch exception generated during provisioning of subscriber

Before exceptions were silently dropped.
Also, rely on MacAddress.NONE definition for checking Mac Address validity.

Change-Id: Iec9d8a38df32708ddb0415a3b5116b7db685ea03
diff --git a/app/src/main/java/org/opencord/olt/impl/OltFlowService.java b/app/src/main/java/org/opencord/olt/impl/OltFlowService.java
index af8ba4a..8e6ad0a 100644
--- a/app/src/main/java/org/opencord/olt/impl/OltFlowService.java
+++ b/app/src/main/java/org/opencord/olt/impl/OltFlowService.java
@@ -97,7 +97,6 @@
     private static final String REMOVAL = "removal";
     private static final String V4 = "V4";
     private static final String V6 = "V6";
-    private static final String NO_MAC = "A4:23:05:00:00:00";
 
     private final Logger log = getLogger(getClass());
 
@@ -614,7 +613,8 @@
         }
 
         if (tagInformation.getConfiguredMacAddress() != null &&
-                !NO_MAC.equals(tagInformation.getConfiguredMacAddress())) {
+                !tagInformation.getConfiguredMacAddress().equals("") &&
+                !MacAddress.NONE.equals(MacAddress.valueOf(tagInformation.getConfiguredMacAddress()))) {
             selectorBuilder.matchEthDst(MacAddress.valueOf(tagInformation.getConfiguredMacAddress()));
         }