dashboard: review migrate form texts

closes #341

circle/dashboard/forms.py

@@ -753,7 +753,12 @@ class VmRenewForm(OperationForm):
 
 class VmMigrateForm(forms.Form):
     live_migration = forms.BooleanField(
-        required=False, initial=True, label=_("live migration"))
+        required=False, initial=True, label=_("Live migration"),
+        help_text=_(
+            "Live migration is a way of moving virtual machines between "
+            "hosts with a service interruption of at most some seconds. "
+            "Please note that it can take very long and cause "
+            "much network traffic in case of busy machines."))
 
     def __init__(self, *args, **kwargs):
         choices = kwargs.pop('choices')

circle/vm/operations.py

@@ -466,8 +466,8 @@ class DestroyOperation(InstanceOperation):
 class MigrateOperation(RemoteInstanceOperation):
     id = 'migrate'
     name = _("migrate")
-    description = _("Move virtual machine to an other worker node with a few "
-                    "seconds of interruption (live migration).")
+    description = _("Move a running virtual machine to an other worker node "
+                    "keeping its full state.")
     required_perms = ()
     superuser_required = True
     accept_states = ('RUNNING', )