[CORD-578] MPLS ECMP configurable

Changes:
- Adds MPLS-ECMP option to SR configuration;
- Updates the json examples;
- Implements unit tests to verify the expected behaviors;

Change-Id: I6a7f5d34161be7c85ecb76c9a09288d960aad3cb
diff --git a/apps/segmentrouting/src/test/resources/xconnect-invalid.json b/apps/segmentrouting/src/test/resources/xconnect-invalid.json
index aa35f31..e468271 100644
--- a/apps/segmentrouting/src/test/resources/xconnect-invalid.json
+++ b/apps/segmentrouting/src/test/resources/xconnect-invalid.json
@@ -15,4 +15,4 @@
       "ports": [4, 5, 6]
     }
   ]
-}
\ No newline at end of file
+}