[test] Add OpenMPT emptyslot.it test case

Signed-off-by: Claudio Matsuoka <cmatsuoka@gmail.com>
[test] Update test data md5 sum

Apparently the IT sample mapping fix affected the binary output of the
test module. Update the md5 data accordingly.

Signed-off-by: Claudio Matsuoka <cmatsuoka@gmail.com>