IPContext merged in begin chain element (#1231)

Using the Client chain, the network service client cannot update the
IPContext without the mergeConnectionContext function implemented. A NSC
might want to update it if it needs to add, update or delete routes, src
IP addresses (VIPs...), policies...

Signed-off-by: Lionel Jouin <lionel.jouin@est.tech>

pkg/networkservice/common/begin/merge.go

@@ -36,7 +36,8 @@ func mergeConnection(returnedConnection, requestedConnection, connection *networ
 func mergeConnectionContext(returnedConnectionContext, requestedConnectionContext, connectioncontext *networkservice.ConnectionContext) *networkservice.ConnectionContext {
 	rv := proto.Clone(connectioncontext).(*networkservice.ConnectionContext)
 	if !proto.Equal(returnedConnectionContext, requestedConnectionContext) {
-		// TODO: IPContext, DNSContext, EthernetContext, do we need to do MTU?
+		// TODO: DNSContext, EthernetContext, do we need to do MTU?
+		rv.IpContext = requestedConnectionContext.IpContext
 		rv.ExtraContext = mergeMapStringString(returnedConnectionContext.GetExtraContext(), requestedConnectionContext.GetExtraContext(), connectioncontext.GetExtraContext())
 	}
 	return rv