Fix test so cqxx incorporated into transverse solve only if second order...

... method is being used -- to agree with code in clawpack/classic/src/2d/flux2.f90

In principle the user should not set 
```
    clawdata.order = 1
    clawdata.transverse_waves = 2
```
since only 0 or 1 make sense for `transverse_waves` in this case, but I just wanted to see do a quick comparison with the 1st order method and forgot to change this.  In the current code it then adds in garbage from cqxx being un-initialized.  This PR fixes this to agree with what's done in the classic code.

The same change needs to be made in geoclaw.

We might also want to modify `clawpack/clawutil/src/python/clawutil/data.py` to put in a warning for this?