Ignoring user-defined solverType in the FSI module

[MakisH]

At least in the FSI module, defining a custom solver type is ignored, at least when in a known type can be deduced.

To reproduce, add a custom solver type in the tutorial quickstart/fluid-openfoam/system/preciceDict:

FSI
{
  rho rho [1 -3 0 0 0 0 0] 1000;
  solverType basic;
}

I encountered this while checking the error handling in the constructor of ForceBase. The solver type is determined in FSI/FSI.C (functions readConfig and configure). Compare with CHT/CHT.C.