Say when a platform cannot report its ntp state

get_ntp_enabled returns None to mean the platform cannot tell us, and that went
to the caller as the literal text "None", which says nothing at all. Report it as
unsupported instead, which the tooling already renders plainly.

confluent_server/confluent/plugins/hardwaremanagement/ipmi.py

@@ -1559,6 +1559,11 @@ class IpmiHandler:
         if self.element[3] == 'enabled':
             if 'read' == self.op:
                 enabled = await self.ipmicmd.get_ntp_enabled()
+                if enabled is None:
+                    # None is how the platform says it cannot tell us, and
+                    # reporting that as the text "None" tells the caller nothing
+                    raise pygexc.UnsupportedFunctionality(
+                        'NTP state is not reported by this platform')
                 await self.output.put(msg.NTPEnabled(self.node, enabled))
                 return
             elif 'update' == self.op: