mfile: output data with correct format

[nak3]

mfile: output data with correct format

When same block but different data exists, it produces error log with
the differnt data. Currently, these data output with string format
even though they are byte data. This patch changes to data format
correctly.

current log output:

2016-12-15 13:12:26.254596 E | storage: , ��33

this patch fixes as:

2016-12-15 13:16:11.139927 E | storage: old: [0 0 0 0 0 0 0 0 0 0], new: [0 0 1 0 0 0 4 0 51 51]