Do not create column if value is empty

Cassandra/pycassa complains if we try to create a column with empty value. We
should create the column only if a valid value is to be written.

Change-Id: Id7810e698d09c98a6a816baf8bf882b6408dd71e
Partial-Bug: 1430089

src/config/schema-transformer/db.py

@@ -12,6 +12,7 @@
 from cfgm_common.zkclient import IndexAllocator
 from cfgm_common.vnc_cassandra import VncCassandraClient
 from sandesh_common.vns.constants import SCHEMA_KEYSPACE_NAME
+import uuid
 
 class SchemaTransformerDB(VncCassandraClient):
 
@@ -214,8 +215,12 @@ def get_service_chain_ip(self, sc_name):
             return None, None
 
     def add_service_chain_ip(self, sc_name, ip, ipv6):
-        self._sc_ip_cf.insert(sc_name, {'ip_address': ip,
-                                        'ipv6_address': ipv6})
+        val = {}
+        if ip:
+            val['ip_address'] = ip
+        if ipv6:
+            val['ipv6_address'] = ipv6
+        self._sc_ip_cf.insert(sc_name, val)
 
     def remove_service_chain_ip(self, sc_name):
         try: