Handle Windows oddity in java's process launch library

One test case slipped through the cracks: Java on Windows. This fixes those test failures.

Verification

[ ] In MSF, check out the new_cmd_exec branch
[ ] Build the java solution (run make when in a directory adjacent to MSF)
[ ] Create a java payload (java/meterpreter/reverse_tcp), and run it on Windows
[ ] Catch the shell in MSF - validate that it warns that 'ext_server_stdapi.jar is being used`
[ ] loadpath test/modules/
[ ] use post/test/cmd_exec
[ ] run with the captured session
[ ] Validate that all tests pass