Add documentation about intricacies of MgmtSrvr::versionNode and ::status

ndb/src/mgmsrv/MgmtSrvr.cpp:
  Document why getOwnNodeID==nodeId is different in ::versionNode
ndb/src/mgmsrv/MgmtSrvr.hpp:
  Document the usage of the address pointer returned from status()

ndb/src/mgmsrv/MgmtSrvr.cpp

@@ -695,6 +695,16 @@ MgmtSrvr::versionNode(int nodeId, Uint32 &version, const char **address)
   version= 0;
   if (getOwnNodeId() == nodeId)
   {
+    /**
+     * If we're inquiring about our own node id,
+     * We know what version we are (version implies connected for mgm)
+     * but would like to find out from elsewhere what address they're using
+     * to connect to us. This means that secondary mgm servers
+     * can list ip addresses for mgm servers.
+     *
+     * If we don't get an address (i.e. no db nodes),
+     * we get the address from the configuration.
+     */
     sendVersionReq(nodeId, version, address);
     version= NDB_VERSION;
     if(!*address)

ndb/src/mgmsrv/MgmtSrvr.hpp

@@ -201,7 +201,13 @@ public:
 
   ~MgmtSrvr();
 
-  int status(int processId, 
+  /**
+   * Get status on a node.
+   * address may point to a common area (e.g. from inet_addr)
+   * There is no gaurentee that it is preserved across calls.
+   * Copy the string if you are not going to use it immediately.
+   */
+  int status(int nodeId,
 	     ndb_mgm_node_status * status,
 	     Uint32 * version,
 	     Uint32 * phase,