[2768] Output seq of message waited for

To help debugging.

src/lib/cc/cc_messages.mes

@@ -37,7 +37,7 @@ socket listed in the output.
 This debug message indicates that the connection was successfully made, this
 should follow CC_ESTABLISH.
 
-% CC_GROUP_RECEIVE trying to receive a message
+% CC_GROUP_RECEIVE trying to receive a message with seq %1
 Debug message, noting that a message is expected to come over the command
 channel.
 

src/lib/cc/session.cc

@@ -498,7 +498,7 @@ bool
 Session::group_recvmsg(ConstElementPtr& envelope, ConstElementPtr& msg,
                        bool nonblock, int seq)
 {
-    LOG_DEBUG(logger, DBG_TRACE_DETAILED, CC_GROUP_RECEIVE);
+    LOG_DEBUG(logger, DBG_TRACE_DETAILED, CC_GROUP_RECEIVE).arg(seq);
     bool result(recvmsg(envelope, msg, nonblock, seq));
     if (result) {
         LOG_DEBUG(logger, DBG_TRACE_DETAILED, CC_GROUP_RECEIVED).