Update muscle tests to use have a valid path (with at least two points)
Update muscle tests to use have a valid path (with at least two points)

opensim-org/opensim-core,opensim-org/opensim-core,opensim-org/opensim-core,opensim-org/opensim-core,opensim-org/opensim-core,opensim-org/opensim-core,opensim-org/opensim-core