Fix ping before connection error

If ping() was called before connect, an exception was raised.  Fix this by
returning false in such an event.

confluent_server/confluent/plugins/hardwaremanagement/ipmi.py

@@ -275,10 +275,13 @@ class IpmiConsole(conapi.Console):
         self.solconnection.send_break()
 
     def ping(self):
+        if not self.solconnection:
+            return False
         rsp = self.solconnection.ipmi_session.raw_command(netfn=6,
                                                           command=0x4b,
                                                           data=(1, 1))
         self.solconnection._got_payload_instance_info(rsp)
+        return True
 
 
 def perform_requests(operator, nodes, element, cfg, inputdata):