[server] bugfix for maxsplit

ref:
aio-libs/aiohttp@9ad54c7

Author: iblislin

couchdb/server/mime.py

@@ -17,7 +17,7 @@ def parse_mimetype(mimetype):
     params = {}
     for item in parts[1:]:
         if '=' in item:
-            key, value = item.split('=', 2)
+            key, value = item.split('=', 1)
         else:
             key, value = item, None
         params[key] = value