adjust Msf::Util::EXE for newer file output

Newer releases of File have a much different output when given a jar
file. Adjust regex per egyp7's suggestion to close bug 8792 on redmine.

Failure/Error: verify_bin_fingerprint(format_hash, bin)
expected: /zip/i
got: "/dev/stdin: Java archive data (JAR)\n" (using =~)

Tested and confirmed working with file 5.17 on Gentoo Linux.