Minor refactoring for fabric.p4

Change-Id: I736b20fc95b4a03afa1074eb777a23507530b44f
diff --git a/pipelines/fabric/src/main/java/org/onosproject/pipelines/fabric/pipeliner/FabricPipeliner.java b/pipelines/fabric/src/main/java/org/onosproject/pipelines/fabric/pipeliner/FabricPipeliner.java
index 3fceb5d..eac586a 100644
--- a/pipelines/fabric/src/main/java/org/onosproject/pipelines/fabric/pipeliner/FabricPipeliner.java
+++ b/pipelines/fabric/src/main/java/org/onosproject/pipelines/fabric/pipeliner/FabricPipeliner.java
@@ -197,8 +197,8 @@
                 .thenApplyAsync(groupSuccess -> groupSuccess && installFlows(objective, flowRules))
                 .thenAcceptAsync(callback)
                 .exceptionally((ex) -> {
-                    log.warn("Got unexpected exception while applying translation result {}",
-                             result);
+                    log.warn("Got unexpected exception while applying translation result {}: {}",
+                             result, ex);
                     fail(objective, ObjectiveError.UNKNOWN);
                     return null;
                 });