fixup: only one pool required for postinstall job

Signed-off-by: Samuel Verschelde <stormi-xcp@ylix.fr>

Author: stormi

jobs.py

@@ -30,7 +30,7 @@ class JobData(TypedDict):
             "pool twice.) Config in data.py for a NFS SR.",
             "A VM (small and fast-booting).",
         ],
-        "nb_pools": 2,
+        "nb_pools": 1,
         "params": {
             "--vm": "single/small_vm",
         },