lib: zlog_hexdump actually output printable ascii characters

lib: zlog_hexdump actually output printable ascii characters

We are getting this output from zlog_hexdump:

0x00007fffdd1f9648: 45 00 00 94 ee 63 40 00 45....6340.
0x00007fffdd1f9650: 03 00 ff 0a 14 00 0f fd ........
0x00007fffdd1f9658: e8 01 01 01 45 00 00 80 ....45...
0x00007fffdd1f9660: ee 63 40 00 0a 11 75 0a .6340...75.
0x00007fffdd1f9668: 14 00 0f fd e8 01 01 01 ........
0x00007fffdd1f9670: 10 e1 10 e1 00 6c d0 54 .....6c.54
0x00007fffdd1f9678: 00 00 00 00 00 00 00 00 ........
0x00007fffdd1f9680: 00 00 00 00 00 00 00 00 ........
0x00007fffdd1f9688: 00 00 00 00 00 00 00 00 ........
0x00007fffdd1f9690: 00 00 00 00 00 00 00 00 ........
0x00007fffdd1f9698: 00 00 00 00 00 00 00 00 ........
0x00007fffdd1f96a0: 00 00 00 00 00 00 00 00 ........
0x00007fffdd1f96a8: 00 00 00 00 00 00 00 00 ........
0x00007fffdd1f96b0: 00 00 00 00 00 00 00 00 ........
0x00007fffdd1f96b8: 00 00 00 00 00 00 00 00 ........
0x00007fffdd1f96c0: 00 00 00 00 00 00 00 00 ........
0x00007fffdd1f96c8: 00 00 00 00 00 00 00 00 ........
0x00007fffdd1f96d0: 00 00 00 00 00 00 00 00 ........
0x00007fffdd1f96d8: 00 00 00 00             ....

As you can see the ascii dump on the right is wrong and not lined
up correctly.  This commit fixes this issue:

0x00007ffcf046f228: 45 00 00 58 c6 36 40 00 E..X.6@.
0x00007ffcf046f230: 03 00 ff 73 14 00 0f fd ...s....
0x00007ffcf046f238: e8 01 01 01 45 00 00 44 ....E..D
0x00007ffcf046f240: c6 36 40 00 0a 11 9d 73 .6@....s
0x00007ffcf046f248: 14 00 0f fd e8 01 01 01 ........
0x00007ffcf046f250: 10 e1 10 e1 00 30 d0 cc .....0..
0x00007ffcf046f258: 00 00 00 00 00 00 00 00 ........
0x00007ffcf046f260: 00 00 00 00 00 00 00 00 ........
0x00007ffcf046f268: 00 00 00 00 00 00 00 00 ........
0x00007ffcf046f270: 00 00 00 00 00 00 00 00 ........
0x00007ffcf046f278: 00 00 00 00 00 00 00 00 ........

Signed-off-by: Donald Sharp <sharpd@cumulusnetworks.com>