Fix loading of unmigrated epoch root in sync mode

Author: cjjdespres

src/lib/consensus/proof_of_stake.ml

@@ -461,7 +461,7 @@ module Make_str (A : Wire_types.Concrete) = struct
       let create_epoch_ledger ~config ~context:(module Context : CONTEXT)
           ~genesis_epoch_ledger =
         let open Context in
-        if Mina_ledger.Ledger.Root.Config.exists_backing config then (
+        if Mina_ledger.Ledger.Root.Config.exists_any_backing config then (
           [%log info]
             ~metadata:
               [ ("config", Mina_ledger.Ledger.Root.Config.to_yojson config) ]

src/lib/mina_ledger/test/test_mina_ledger.ml

@@ -115,7 +115,7 @@ module Root_test = struct
         in
         L.Root.Config.move_backing_exn ~src:config ~dst:config_moved ;
         assert (
-          (not (L.Root.Config.exists_backing config))
+          (not (L.Root.Config.exists_any_backing config))
           && L.Root.Config.exists_backing config_moved
           || failwith "Config is not moved" ) ;
         let root_moved =