feat(instances): the VM lists follow changes by themselves

A VM list showed what it read when it was loaded: a VM stopped from
inside its guest or with virsh, or made or removed elsewhere, showed only
after a reload, unlike the VM page, which reloads when its VM's state
changes. The lists of all VMs and of one host's VMs now poll the states
of their VMs, at once and then every 5 s as the VM page does, and reload
when an answer differs from the one before. The states come from one
libvirt call per host; a user who does not see hosts gets only their own
VMs. The page in use (a dialog, a field, an unsaved XML edit, a job
outcome shown) holds the reload until it is free; that check is shared
with the job panel.

vrtManager/connection.py

@@ -1011,6 +1011,11 @@ class wvmConnect(object):
             instances.append(name)
         return instances
 
+    def get_domain_states(self):
+        """{uuid: [name, state]} of every domain, in one call."""
+        return {dom.UUIDString(): [dom.name(), stats["state.state"]]
+                for dom, stats in self.wvm.getAllDomainStats(libvirt.VIR_DOMAIN_STATS_STATE)}
+
     def domain_trees(self, running_only=False):
         """Each domain's name with its definitions, parsed: the live one, and
         for a persistent domain the one saved for its next boot too, read