admin: add build ignore tag to tests that don't compile

These tests aren't included in the top level test script so have
unintentionally been ignored and currently don't compile. Until
this is fixed (see #257) add a build tag so tools ignore them.

admin/api_test.go

+// NOTE: These tests are begin updated so they compile (see #257). Until then ignore.
+// +build ignore
+
 package admin
 
 import (