rust/ike: suppress some compile warnings when not debug

Due to ef5755338f, the variables
that are only used for debug output now emit unused variable
warnings when Suricata is not built with debug. Prefix these
variables with _ to suppress these warnings.

rust/src/ikev2/ikev2.rs

@@ -176,8 +176,8 @@ impl IKEV2State {
                                         self.dh_group = kex.dh_group;
                                     }
                                 },
-                                IkeV2PayloadContent::Nonce(ref n) => {
-                                    SCLogDebug!("Nonce: {:?}", n);
+                                IkeV2PayloadContent::Nonce(ref _n) => {
+                                    SCLogDebug!("Nonce: {:?}", _n);
                                 },
                                 IkeV2PayloadContent::Notify(ref n) => {
                                     SCLogDebug!("Notify: {:?}", n);
@@ -205,7 +205,7 @@ impl IKEV2State {
                             }
                         };
                     },
-                    e => { SCLogDebug!("parse_ikev2_payload_with_type: {:?}",e); () },
+                    _e => { SCLogDebug!("parse_ikev2_payload_with_type: {:?}", _e); () },
                 }
                 1
             },
@@ -330,8 +330,8 @@ impl IKEV2State {
                             _ => (),
                         }
                     },
-                    IkeV2Transform::Unknown(tx_type,tx_id) => {
-                        SCLogDebug!("Unknown proposal: type={:?}, id={}", tx_type, tx_id);
+                    IkeV2Transform::Unknown(_tx_type, _tx_id) => {
+                        SCLogDebug!("Unknown proposal: type={:?}, id={}", _tx_type, _tx_id);
                         self.set_event(IKEV2Event::UnknownProposal);
                     },
                     _ => (),