detect: Workaround serial info for ib<x> devices

When using ipoverib, lshw is getting a truncated information about the
serial.

For the same device we have the current situation,
ifconfig : ib1 Link encap:UNSPEC  HWaddr 80-00-00-49-FE-80-00-00-00-00-00-00-00-00-00-00
lshw     : <serial>80:00:00:49:fe:80</serial>
ip       : link/infiniband 80:00:00:49:fe:80:00:00:00:00:00:00:00:02:c9:03:00:ea:71:82

The point here is both lshw & ifconfig are getting a truncated data that
leads to a duplicated info as both provides the same serial for all ib
interfaces like :

ib0 Link encap:UNSPEC  HWaddr 80-00-00-48-FE-80-00-00-00-00-00-00-00-00-00-00
ib1 Link encap:UNSPEC  HWaddr 80-00-00-49-FE-80-00-00-00-00-00-00-00-00-00-00

This is an issue since we cannot use this information as a descrimiting
information.

Let's workaround by using ip when device is an ib one.

A typical result is now:
 ('network',
  'ib1',
  'serial',
  '80:00:00:49:fe:80:00:00:00:00:00:00:00:02:c9:03:00:ea:71:82'),