Fix server session to properly support rqlun

Honor rqlun from client, if not zero.  There are BMC implementations
that fail to follow the spec and do rqlun of zero, but pyghmi
implements it correctly.  In practice I have never seen an
rqlun of non-zero except as an experiment.

Closes-Bug: #1865987

Change-Id: I73e59672ce5e146cf24386c2228fa8dae3bc579c

pyghmi/ipmi/private/serversession.py

@@ -72,6 +72,7 @@ class ServerSession(ipmisession.Session):
         self.sessionid = 0
         self.bmc = bmc
         self.lastpayload = None
+        self.rqlun = None  # This will be provided by the client
         self.broken = False
         self.authtype = 6
         self.integrityalgo = 0

pyghmi/ipmi/private/session.py

@@ -1626,6 +1626,7 @@ class Session(object):
             self.seqlun = payload[4] >> 2
             self.clientaddr = payload[3]
             self.clientnetfn = (payload[1] >> 2) + 1
+            self.rqlun = payload[4] & 0b11
             self.clientcommand = payload[5]
             self._parse_payload(payload)
             return