update bw to 4.3, add .provides() to metadata reactors

bundles/backup-server/metadata.py

@@ -7,7 +7,9 @@ defaults = {
     },
 }
 
-@metadata_reactor
+@metadata_reactor.provides(
+    'backup-server/clients',
+)
 def get_my_clients(metadata):
     my_clients = {}
 
@@ -26,7 +28,10 @@ def get_my_clients(metadata):
     }
 
 
-@metadata_reactor
+@metadata_reactor.provides(
+    'zfs/datasets',
+    'zfs/snapshots/retain_per_dataset',
+)
 def zfs(metadata):
     zfs_datasets = {}
     zfs_retains = {}