fix(sdk/client): reserve the host protocal (http or https) so that http host can work. Fixes #4277 (#4285)

sdk/python/kfp/_client.py

@@ -147,11 +147,8 @@ class Client(object):
 
     host = host or ''
     # Preprocess the host endpoint to prevent some common user mistakes.
-    # This should only be done for non-IAP cases (when client_id is None). IAP requires preserving the protocol.
     if not client_id:
-      # Per feedback in proxy env, http or https is still required
-      if not proxy:
-        host = re.sub(r'^(http|https)://', '', host)
+      # always preserving the protocol (http://localhost requires it)
       host = host.rstrip('/')
 
     if host: