Minor tweak to mbuf_probe argument handling to match the 3.5 work.

src/drv/mbuf/mbuf_probe/mbuf_probe.cc

@@ -198,7 +198,7 @@ parse_options( int argc, char* argv[] )
         else
         {
             std::map< std::string, MBufCommands >::iterator it;
-            it = command_lookup.find( args.front( ) );
+            it = command_lookup.find( arg );
             if ( it == command_lookup.end( ) )
             {
                 std::ostringstream os;
@@ -374,4 +374,4 @@ main( int argc, char* argv[] )
         break;
     }
     return 0;
-}
+}
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