ASSERT in vmareas.c in client.nudge_test

In addition to the #4074 (closed) assert and #4075 (closed) deadlock I have also seen this pre-nudge in client.nudge_test:

thank you for testing the client interface
<Application D:\derek\dr\git\build_x86_dbg_tests\suite\tests\bin\win32.infloop.exe (9816).  Internal Error: DynamoRIO debug check failure: D:\derek\dr\git\src\core\vmareas.c:8313 !ok || !TEST(MEMPROT_WRITE, prot2) || TEST(FRAG_SELFMOD_SANDBOXED, *flags) || !INTERNAL_OPTION(hw_cache_consistency)