BGP support default IPV4 unicast capability.

Change-Id: Id9ad101e82a9148ddf029fdcf6404173a9574539
diff --git a/protocols/bgp/bgpio/src/main/java/org/onosproject/bgpio/protocol/ver4/BgpOpenMsgVer4.java b/protocols/bgp/bgpio/src/main/java/org/onosproject/bgpio/protocol/ver4/BgpOpenMsgVer4.java
index 2cc9f7a..76f54fe 100644
--- a/protocols/bgp/bgpio/src/main/java/org/onosproject/bgpio/protocol/ver4/BgpOpenMsgVer4.java
+++ b/protocols/bgp/bgpio/src/main/java/org/onosproject/bgpio/protocol/ver4/BgpOpenMsgVer4.java
@@ -292,6 +292,7 @@
         private short asNumber;
         private boolean isBgpIdSet = false;
         private int bgpId;
+        private boolean isIpV4UnicastCapabilityTlvSet = true;
         private boolean isLargeAsCapabilityTlvSet = false;
         private boolean isLsCapabilityTlvSet = false;
         private boolean isFlowSpecCapabilityTlvSet = false;
@@ -312,6 +313,13 @@
                 throw new BgpParseException("BGPID  is not set (mandatory)");
             }
 
+            if (this.isIpV4UnicastCapabilityTlvSet) {
+                BgpValueType tlv;
+                tlv = new MultiProtocolExtnCapabilityTlv((short) Constants.AFI_IPV4_UNICAST, RES,
+                                                         (byte) Constants.SAFI_IPV4_UNICAST);
+                this.capabilityTlv.add(tlv);
+            }
+
             if (this.isLargeAsCapabilityTlvSet) {
                 BgpValueType tlv;
                 int value = this.asNumber;