kvm: Add a call to thread->startup() in startup()

It is now required to initialize the thread context by calling
startup() on it. Failing to do so currently causes decoder in
x86-based CPUs to get very confused when restoring from checkpoints.

src/cpu/kvm/base.cc

@@ -171,6 +171,8 @@ BaseKvmCPU::startup()
     } else {
         inform("KVM: Coalesced not supported by host OS\n");
     }
+
+    thread->startup();
 }
 
 void