Normalize scan to async

Also, for lots of pending nodes, yield between nodes for responsiveness

confluent_server/confluent/discovery/core.py

@@ -716,6 +716,7 @@ async def _recheck_nodes_backend(nodeattribs, configmanager):
     # now we go through ones that were identified, but could not pass
     # policy or hadn't been able to verify key
     for nodename in pending_nodes:
+        await asyncio.sleep(0)
         info = pending_nodes[nodename]
         try:
             if info['handler'] is None:

confluent_server/confluent/discovery/handlers/generic.py

@@ -96,7 +96,7 @@ class NodeHandler(object):
         # A no-op by default
         return
 
-    def scan(self):
+    async def scan(self):
         # Do completely passive things to enhance data.
         # Probe is permitted to for example attempt a login
         # scan *only* does what it can without a login attempt

confluent_server/confluent/discovery/handlers/imm.py

@@ -28,7 +28,7 @@ class NodeHandler(bmchandler.NodeHandler):
         # This is not adequate for being satisfied
         return bool(info.get('attributes', {}))
 
-    def scan(self):
+    async def scan(self):
         slpattrs = self.info.get('attributes', {})
         self.isdense = False
         try:
@@ -75,7 +75,7 @@ class NodeHandler(bmchandler.NodeHandler):
 
     async def probe(self):
         if self.info.get('enclosure.bay', 0) == 0:
-            self.scan()
+            await self.scan()
         if self.info.get('enclosure.bay', 0) != 0:
             # scan has already populated info
             return

confluent_server/confluent/discovery/handlers/smm.py

@@ -72,7 +72,7 @@ class NodeHandler(bmchandler.NodeHandler):
     devname = 'SMM'
     maxmacs = 14  # support an enclosure, but try to avoid catching daisy chain
 
-    def scan(self):
+    async def scan(self):
         # the UUID is in a weird order, fix it up to match
         # ipmi return and property value
         uuid = self.info.get('attributes', {}).get('uuid', None)

confluent_server/confluent/discovery/handlers/smm3.py

@@ -22,7 +22,7 @@ class NodeHandler(redfishbmc.NodeHandler):
     maxmacs = 18  # support an enclosure, but try to avoid catching daisy chain
     is_enclosure = True
 
-    def scan(self):
+    async def scan(self):
         attrs = self.info.get('attributes', {})
         mtm = attrs.get('enclosure-machinetype-model', None)
         if mtm: