RESTRICT AUTOMERGE Add test for attaching null application thread

Test that the operation will be rejected. This ensures a process
record won't have unexpected state temporally which may disturb
the condition to check caller information.

Bug: 144285917
Test: bit CtsSecurityTestCases:ActivityManagerTest# \
      testActivityManager_attachNullApplication
Change-Id: Ib774109ff54c871cd37eb00a9db11a28a5109053