mpmd: Export RPC token and mb_args to the property tree

There are applications (typically for debugging purposes) which need
access to the token and the mb_args. They are thus published via the
property tree.

host/lib/usrp/mpmd/mpmd_impl.hpp

@@ -131,6 +131,12 @@ public:
         _allow_claim_failure_flag = allow;
     }
 
+    //! Read the device access token
+    std::string get_token()
+    {
+        return _token;
+    }
+
 private:
     /*! Reference to the RPC client that handles claiming
      */
@@ -165,6 +171,10 @@ private:
      */
     uhd::task::sptr _claimer_task;
 
+    /*! A copy of the device access token
+     */
+    std::string _token;
+
     /*! This flag is only used within the claim() function. Go look there if you
      * really need to know what it does.
      */

host/lib/usrp/mpmd/mpmd_mboard_impl.cpp

@@ -379,6 +379,7 @@ uhd::task::sptr mpmd_mboard_impl::claim_device_and_make_task()
     // Save token for both RPC clients
     _claim_rpc->set_token(rpc_token);
     rpc->set_token(rpc_token);
+    _token = rpc_token;
     // Optionally clear log buf
     if (mb_args.has_key("skip_oldlog")) {
         try {