migration: Fix seg with missing port

The command :
   migrate tcp:localhost:

   currently segs; fix it so it now says:

   error parsing address 'localhost:'

and the same for -incoming.
Signed-off-by: NDr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: NDaniel P. Berrange <berrange@redhat.com>
Reviewed-by: NJuan Quintela <quintela@redhat.com>
Signed-off-by: NJuan Quintela <quintela@redhat.com>

migration/socket.c

@@ -112,8 +112,12 @@ void tcp_start_outgoing_migration(MigrationState *s,
                                   const char *host_port,
                                   Error **errp)
 {
-    SocketAddress *saddr = tcp_build_address(host_port, errp);
-    socket_start_outgoing_migration(s, saddr, errp);
+    Error *err = NULL;
+    SocketAddress *saddr = tcp_build_address(host_port, &err);
+    if (!err) {
+        socket_start_outgoing_migration(s, saddr, &err);
+    }
+    error_propagate(errp, err);
 }
 
 void unix_start_outgoing_migration(MigrationState *s,
@@ -174,8 +178,12 @@ static void socket_start_incoming_migration(SocketAddress *saddr,
 
 void tcp_start_incoming_migration(const char *host_port, Error **errp)
 {
-    SocketAddress *saddr = tcp_build_address(host_port, errp);
-    socket_start_incoming_migration(saddr, errp);
+    Error *err = NULL;
+    SocketAddress *saddr = tcp_build_address(host_port, &err);
+    if (!err) {
+        socket_start_incoming_migration(saddr, &err);
+    }
+    error_propagate(errp, err);
 }
 
 void unix_start_incoming_migration(const char *path, Error **errp)