Convert the ThreadPlanCommands test to use a scripted plan

that pushes a step over plan.  Relax the listing checker
so it will look past any entries after the ones listed in
the input patterns.  Then for the internal plans just check
for the StepOver plan that our scripted plan pushes, and look past
any others.

This should make the test more robust on systems that don't use the
step-in then push a step-out plan to step over a function.