Handle Windows oddity in java's process launch library

[smashery]

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

[adfoster-r7]

Automated tests passing when pointing rapid7/metasploit-framework#19108 to this pull request