test/mi: Improve test OK reporting, print log data separately

test/mi: Improve test OK reporting, print log data separately

Currently, we have a confusing output for tests (all of which currenly
pass):

    $ ./obj/test/test-mi
    crc mismatch
    $ echo $?
    0

This change adds reporting for each test, and separates the nvme_msg log
data from the report:

    $ ./obj/test/test-mi
    Running test read_mi_data...  OK
    Running test transport_fail...  OK
    Running test invalid_crc...  OK
    --- begin test output
    crc mismatch
    --- end test output

Signed-off-by: Jeremy Kerr <jk@codeconstruct.com.au>