GUIAgent does not properly handle "star" meshes

[arlake228]

If you use a "star" group in your mesh diefinition the GUIAgent gives the following error:

2017/05/09 09:36:02 (1781) ERROR> GUIAgent.pm:258 perfSONAR_PS::MeshConfig::GUIAgent::__generate_maddash_config - Problem generating maddash configuration: Can't locate object method "center_address" via package "perfSONAR_PS::MeshConfig::Config::Group::Disjoint" at /root/mesh-config/bin/../lib/perfSONAR_PS/MeshConfig/Generators/MaDDash.pm line 243.

Star has always been a special type and looks like it is converted to disjoint before the block of code in question is hit, so no center_address value.