Steady state solver deadlocks at convergence in oversetFE

[adityakpandare]

The steady state oversetFE solver deadlocks when only one of the meshes reaches the convergence criterion (residual < tol). This is potentially because the mesh that converged sets m_finished = 1, but the other mesh (correctly) doesn't, and follows a different code-path. The correct thing to do is to check the convergence criterion on all meshes, and only then declare convergence (i.e. set m_finished = 1) on all meshes. This check will have to be done in Transporter::diagnostics().