sw test tool: Improve readability of MAC mask values

    1099511627775
->  "00:ff:ff:ff:ff:ff"

    281474976710400
->  "ff:ff:ff:ff:ff:00"

    281474959998975
->  "ff:ff:ff:00:ff:ff"

    281470698520575
->  "ff:ff:00:ff:ff:ff"

Signed-off-by: Yuichi Ito <ito.yuichi0@gmail.com>
sw test tool: Improve readability of IP mask values

    4294967040
->  "255.255.255.0"

    4294902015
->  "255.255.0.255"

    340282366920938463463374607431768145920
->  "ffff:ffff:ffff:ffff:ffff:ffff:ffff:0"

    5192296858534827628530496329220095
->  "0:ffff:ffff:ffff:ffff:ffff:ffff:ffff"

Signed-off-by: Yuichi Ito <ito.yuichi0@gmail.com>