vet: Fix format string warnings

Signed-off-by: Euan Harris <euan.harris@docker.com>

libnetwork/drivers/bridge/setup_ip_tables.go

@@ -302,7 +302,7 @@ func setINC(iface string, enable bool) error {
 				if i == 1 {
 					// Rollback the rule installed on first chain
 					if err2 := iptables.ProgramRule(iptables.Filter, chains[0], iptables.Delete, rules[0]); err2 != nil {
-						logrus.Warn("Failed to rollback iptables rule after failure (%v): %v", err, err2)
+						logrus.Warnf("Failed to rollback iptables rule after failure (%v): %v", err, err2)
 					}
 				}
 				return fmt.Errorf(msg)

libnetwork/network.go

@@ -1054,7 +1054,7 @@ func (n *network) delete(force bool, rmLBEndpoint bool) error {
 					t.Name(), n.Name(), err)
 			}
 		} else {
-			logrus.Warnf("Could not find configuration network %q during removal of network %q", n.configOnly, n.Name())
+			logrus.Warnf("Could not find configuration network %q during removal of network %q", n.configFrom, n.Name())
 		}
 	}