KVM: fix RebootInstance

RebootInstance was broken, because it just used to call StartInstance
with wrong parameters. With this patch we still stop the instance, but
use the saved kvm runtime to start it again.

Reviewed-by: iustinp

lib/hypervisor/hv_kvm.py

@@ -393,8 +393,16 @@ class KVMHypervisor(hv_base.BaseHypervisor):
     # For some reason if we do a 'send-key ctrl-alt-delete' to the control
     # socket the instance will stop, but now power up again. So we'll resort
     # to shutdown and restart.
-    self.StopInstance(instance)
-    self.StartInstance(instance)
+
+    # StopInstance will delete the saved KVM runtime so:
+    # ...first load it...
+    kvm_runtime = self._LoadKVMRuntime(instance)
+    # ...now we can safely call StopInstance...
+    if not self.StopInstance(instance):
+      self.StopInstance(instance, force=True)
+    # ...and finally we can save it again, and execute it...
+    self._SaveKVMRuntime(instance, kvm_runtime)
+    self._ExecuteKVMRuntime(instance, kvm_runtime)
 
   def GetNodeInfo(self):
     """Return information about the node.