PX4 package depends on mav_msgs

It already uses it in the cmakelists, but was missing a dependency in
the package.xml.

package.xml

@@ -47,12 +47,14 @@
   <build_depend>libmavconn</build_depend>
   <build_depend>tf</build_depend>
   <build_depend>rostest</build_depend>
+  <build_depend>mav_msgs</build_depend>
   <run_depend>roscpp</run_depend>
   <run_depend>rospy</run_depend>
   <run_depend>std_msgs</run_depend>
   <run_depend>eigen</run_depend>
   <run_depend>libmavconn</run_depend>
   <run_depend>tf</run_depend>
+  <run_depend>mav_msgs</run_depend>
 
 
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