Adding default as_path for 2 byte asn neighbor

With 4 byte asn changes, by default as_path with 4 byte asn
was being added. It should be as_path with 2 byte asn if the
peer does not support 4 byte asn.

Change-Id: Ic1cf113613a36615797cb985b1a3f4199e2fd663
Closes-Bug: #218663

src/bgp/bgp_table.cc

@@ -25,9 +25,7 @@
 #include "bgp/tunnel_encap/tunnel_encap.h"
 #include "net/community_type.h"
 
-using std::map;
 using std::make_pair;
-using std::ostringstream;
 using std::string;
 
 class BgpTable::DeleteActor : public LifetimeActor {
@@ -586,10 +584,14 @@ UpdateInfo *BgpTable::GetUpdateInfo(RibOut *ribout, BgpRoute *route,
             // then generate a Nil AsPath i.e. one with 0 length. No need
             // to modify the AsPath if it already exists since this is an
             // iBGP RibOut.
-            if (clone->aspath_4byte() == NULL) {
+            if (ribout->as4_supported() && !clone->aspath_4byte()) {
                 AsPath4ByteSpec as_path;
                 clone->set_aspath_4byte(&as_path);
             }
+            if (!ribout->as4_supported() && !clone->as_path()) {
+                AsPathSpec as_path;
+                clone->set_as_path(&as_path);
+            }
         } else if (ribout->peer_type() == BgpProto::EBGP) {
             // Don't advertise routes from non-master instances if there's
             // no nexthop. The ribout has to be for bgpaas-clients because