fix member initialization order

to stop spam from https://build.ros.org/job/Mdev__tsid__ubuntu_bionic_amd64/

src/tasks/task-cop-equality.cpp

@@ -27,8 +27,8 @@ namespace tasks
 
 TaskCopEquality::TaskCopEquality(const std::string & name, RobotWrapper & robot):
 TaskContactForce(name, robot),
-m_constraint(name, 3, 3),
-m_contact_name("")
+m_contact_name(""),
+m_constraint(name, 3, 3)
 {
   m_normal << 0, 0, 1;
 }