Do not rename in decode_par2 if the filename didn't change

Closes #1952

sabnzbd/deobfuscate_filenames.py

@@ -64,9 +64,9 @@ def decode_par2(parfile: str) -> List[str]:
             with open(filepath, "rb") as fileToMatch:
                 first16k_data = fileToMatch.read(16384)
 
-            # Check if we have this hash
+            # Check if we have this hash and the filename is different
             file_md5of16k = hashlib.md5(first16k_data).digest()
-            if file_md5of16k in md5of16k:
+            if file_md5of16k in md5of16k and fn != md5of16k[file_md5of16k]:
                 new_path = os.path.join(dirname, md5of16k[file_md5of16k])
                 # Make sure it's a unique name
                 unique_filename = get_unique_filename(new_path)