RFR (XS): 8004691: Add a jtreg test that exercises the ExecuteInternalVMTests flag

[Erik Helin]

Hi all,

this change adds a jtreg test that runs the internal vm tests.

Webrev:
http://cr.openjdk.java.net/~ehelin/8004691/webrev.00/

Summary:
There are a couple of tests in HotSpot C++ source code that can be run
with the flag -XX:+ExecuteInternalVMTests. These tests are run in JPRT
queues, but they are not run as part of the nightly testing.

This change adds an empty jtreg test that starts the VM with the flag
-XX:+ExecuteInternalVMTests, thereby running the internal VM tests.

Since -XX:+ExecuteInternalVMTests only works with a non-product build of
the VM, the test also uses the flag -XX:+IgnoreUnrecognizedVMOptions to
make sure the test works, but does nothing, when run with a product
build of HotSpot.

Testing:
JPRT

Thanks,
Erik