rust: simply matches with unwrap_or_default

New default clippy warning:
https://rust-lang.github.io/rust-clippy/master/index.html#manual_unwrap_or_default

rust/src/smb/dcerpc.rs

@@ -455,10 +455,7 @@ pub fn smb_read_dcerpc_record(state: &mut SMBState,
     // msg_id 0 as this data crosses cmd/reply pairs
     let ehdr = SMBHashKeyHdrGuid::new(SMBCommonHdr::new(SMBHDR_TYPE_TRANS_FRAG,
             hdr.ssn_id, hdr.tree_id, 0_u64), guid.to_vec());
-    let mut prevdata = match state.ssnguid2vec_map.remove(&ehdr) {
-        Some(s) => s,
-        None => Vec::new(),
-    };
+    let mut prevdata = state.ssnguid2vec_map.remove(&ehdr).unwrap_or_default();
     SCLogDebug!("indata {} prevdata {}", indata.len(), prevdata.len());
     prevdata.extend_from_slice(indata);
     let data = prevdata;

rust/src/smb/smb1.rs

@@ -891,11 +891,8 @@ pub fn smb1_trans_response_record(state: &mut SMBState, r: &SmbRecord)
             SCLogDebug!("TRANS response {:?}", rd);
 
             // see if we have a stored fid
-            let fid = match state.ssn2vec_map.remove(
-                    &SMBCommonHdr::from1(r, SMBHDR_TYPE_GUID)) {
-                Some(f) => f,
-                None => Vec::new(),
-            };
+            let fid = state.ssn2vec_map.remove(
+                    &SMBCommonHdr::from1(r, SMBHDR_TYPE_GUID)).unwrap_or_default();
             SCLogDebug!("FID {:?}", fid);
 
             let mut frankenfid = fid.to_vec();

rust/src/smb/smb2.rs

@@ -679,13 +679,7 @@ pub fn smb2_response_record(state: &mut SMBState, r: &Smb2Record)
                         /* search key-guid map */
                         let guid_key = SMBCommonHdr::new(SMBHDR_TYPE_GUID,
                                 r.session_id, r.tree_id, r.message_id);
-                        let _guid_vec = match state.ssn2vec_map.remove(&guid_key) {
-                            Some(p) => p,
-                            None => {
-                                SCLogDebug!("SMBv2 response: GUID NOT FOUND");
-                                Vec::new()
-                            },
-                        };
+                        let _guid_vec = state.ssn2vec_map.remove(&guid_key).unwrap_or_default();
                         SCLogDebug!("SMBv2 write response for GUID {:?}", _guid_vec);
                     }
                     _ => {