Enable checkstyle rule for missing defaults in switch statements

Enabled the checkstyle rule that looks for switch statements that
don't have a default label and fixed the violations that were
found.

Code review results for switch statement default branches

Change-Id: I68716894952835def659b4fcab5b381aaf9ff89e
diff --git a/src/main/java/net/onrc/onos/apps/bgproute/BgpRoute.java b/src/main/java/net/onrc/onos/apps/bgproute/BgpRoute.java
index b766448..303f198 100644
--- a/src/main/java/net/onrc/onos/apps/bgproute/BgpRoute.java
+++ b/src/main/java/net/onrc/onos/apps/bgproute/BgpRoute.java
@@ -1255,6 +1255,9 @@
                                         update.getPrefix(), update.getRibEntry().getNextHop());
                             }
                             break;
+                        default:
+                            log.error("Unknown operation {}", update.getOperation());
+                            break;
                     }
                 } catch (InterruptedException e) {
                     log.debug("Interrupted while taking from updates queue", e);