Inprocess: Users still get the 500 error after putting app_offline.htm to out-of-process application, leaving a single in-process application alone

[jhkimnew]

STEPS TO REPRO:

1. Create two apps Foo and Bar
2. Set OutOfProcess for Foo and InProcess for Bar
3. Send request to Foo and users should get 200
4. Send request to Bar and users should get 500 because ANCM does not support mixed process mode
5. Put app_offline.htm to Foo to make the Foo application gone
6. Send request to Bar

EXPECTED

users should get 200

ACTUAL:

Users still get 500 even though there is only Bar application Even users get 503 even from Foo application.