Update src/rviz/default_plugin/interactive_markers/interactive_marker_control.cpp

added check to see if mouse_dragging_ is true (which would mean we are dragging the mouse) before calling mouseMoveEvent callback.
This fixes a problem where the right clicking on an interactive marker to bring up a menu and then clicking on the marker with the left button would drag the marker as though the mouse had dragged from the point of the right click.