dcerpc: set endian flag after applying transforms

dcerpc_tx_get_stub_data set the DCE byte-order flag before
SCInspectionBufferSetupAndApplyTransforms. Once a later commit makes
buffer setup reset the flags, that order would clear the flag and
break byte_test's dce option (dcerpc/dcerpc-dcepayload-15).

Set the flag after the call.

Issue: 7313

rust/src/dcerpc/detect.rs

@@ -1,4 +1,4 @@
-/* Copyright (C) 2020 Open Information Security Foundation
+/* Copyright (C) 2020-2026 Open Information Security Foundation
  *
  * You can copy, redistribute or modify this Program under the terms of
  * the GNU General Public License version 2 as published by the Free
@@ -426,15 +426,15 @@ unsafe extern "C" fn dcerpc_tx_get_stub_data(
                 tx.stub_data_buffer_tc.len() as u32,
             )
         };
+        SCInspectionBufferSetupAndApplyTransforms(
+            det_ctx, list_id, buffer, data, data_len, transforms,
+        );
+
         if tx.endianness > 0 {
             (*buffer).flags |= DETECT_CI_FLAGS_DCE_LE;
         } else {
             (*buffer).flags |= DETECT_CI_FLAGS_DCE_BE;
         }
-
-        SCInspectionBufferSetupAndApplyTransforms(
-            det_ctx, list_id, buffer, data, data_len, transforms,
-        );
     }
     return buffer;
 }