Fix the build (#85)

Author: David Hotham

framework/src/config/config_reader.rs

@@ -296,6 +296,7 @@ pub fn read_configuration_from_str(configuration: &str, filename: &str) -> Resul
         pool_size: pool_size,
         cache_size: cache_size,
         ports: ports,
+        dpdk_args: None,
     })
 }
 

framework/src/config/mod.rs

@@ -74,7 +74,7 @@ impl fmt::Display for NetbricksConfiguration {
         for core in &self.cores {
             try!(write!(f, "\t{}\n", core))
         }
-        if let Some(arg) = self.dpdk_args {
+        if let Some(ref arg) = self.dpdk_args {
             write!(f, "DPDK Args: {}\n", arg)?
         };
         write!(f, "")