Add test cases for #14750

Author: michaelklishin

deps/rabbit/test/config_schema_SUITE_data/rabbit.snippets

@@ -17,6 +17,14 @@
   "auth_backends.1 = oauth2",
   [{rabbit,[{auth_backends,[rabbit_auth_backend_oauth2]}]}],
   []},
+ {internal_auth_backend,
+  "auth_backends.1 = internal",
+  [{rabbit,[{auth_backends,[rabbit_auth_backend_internal]}]}],
+  []},
+ {internal_loopback_auth_backend,
+  "auth_backends.1 = internal_loopback",
+  [{rabbit,[{auth_backends,[rabbit_auth_backend_internal_loopback]}]}],
+  []},
  {multiple_auth_backends,
  "auth_backends.1 = ldap
 auth_backends.2 = internal",