Gracefully handle not being able to remove oruself from list

NodeInstance.py

@@ -99,7 +99,7 @@ class NodeInstance(threading.Thread):
             for domain, instance in self.s_domain.items():
                 instance.manage_vm_state()
 
-            # Remove non-running VMs from our list
+            # Remove any non-running VMs from our list
             for domain in self.domain_list:
                 try:
                     buuid = uuid.UUID(domain).bytes

VMInstance.py

@@ -56,14 +56,20 @@ class VMInstance:
         print("Forcibly stopping VM %s" % self.domuuid)
         self.dom.destroy()
         if self.domuuid in self.thishypervisor.domain_list:
+            try:
                 self.thishypervisor.domain_list.remove(self.domuuid)
+            except ValueError:
+                pass
     
     # Shutdown the VM gracefully
     def shutdown_vm(self):
         print("Stopping VM %s" % self.domuuid)
         self.dom.shutdown()
         if self.domuuid in self.thishypervisor.domain_list:
+            try:
                 self.thishypervisor.domain_list.remove(self.domuuid)
+            except ValueError:
+                pass
 
     # Migrate the VM to a target host
     def migrate_vm(self):