Refactor & fixup interpreter implementation of tail calls

compiler/rustc_const_eval/src/interpret/step.rs

@@ -32,7 +32,7 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
             // We are unwinding and this fn has no cleanup code.
             // Just go on unwinding.
             trace!("unwinding: skipping frame");
-            self.pop_stack_frame(/* unwinding */ true)?;
+            self.return_from_current_stack_frame(/* unwinding */ true)?;
             return Ok(true);
         };
         let basic_block = &self.body().basic_blocks[loc.block];