Discard all remaining planned blocks with AbortPlannedMoves

Previously it looked like only the active block has been discarded
which worked most of the time, since we only planned single moves.
But with introduction of PlanLongMove in one of the last commits
this is not true anymore.

src/modules/pulse_gen.cpp

@@ -154,7 +154,8 @@ void PulseGen::AbortPlannedMoves(bool halt) {
     if (current_block) {
         last_rate = acc_step_rate;
         current_block = nullptr;
-        block_index.pop();
+        while (!block_index.empty()) // drop all remaining blocks
+            block_index.pop();
     }
 
     // truncate the last rate if halting