Add live migrate max downtime selector meta field

Adds a new flag to VM metadata to allow setting the VM live migration
max downtime. This will enable very busy VMs that hang live migration to
have this value changed.

pvc.sample.conf

@@ -168,7 +168,7 @@ database:
     port: 6379
 
     # Hostname; use `cluster` network floating IP address
-    hostname: 10.0.1.250
+    hostname: 127.0.0.1
 
     # Path, usually "/0"
     path: "/0"
@@ -180,7 +180,7 @@ database:
     port: 5432
 
     # Hostname; use `cluster` network floating IP address
-    hostname: 10.0.1.250
+    hostname: 127.0.0.1
 
     # Credentials
     credentials: