VOM: logging, populate and stats fixes

logging: allow a client to register a callback handler to recieve log messages
         that way the client can maintain a correctly sequenced log
populate: fix the creation of interface and the setting of the handle
stats: the reset promise idea is not defined behaviour.
       Use an eanble/disable command pair

Change-Id: I347720bb65df2874c7619e722d593bc863ee2bf1
Signed-off-by: Neale Ranns <neale.ranns@cisco.com>
diff --git a/src/vpp-api/vom/rpc_cmd.hpp b/src/vpp-api/vom/rpc_cmd.hpp
index ae3c675..bd78978 100644
--- a/src/vpp-api/vom/rpc_cmd.hpp
+++ b/src/vpp-api/vom/rpc_cmd.hpp
@@ -79,7 +79,7 @@
      * we reset the promise after setting the value to reuse it
      * when we run the retire command from the same cmd object
      */
-    m_promise = std::promise<DATA>();
+    //    m_promise = std::promise<DATA>();
   }
 
   /**