bonding: network device names are case sensative

The bonding device acts unlike all other Linux network device functions
in that it ignores case of device names. The developer must have come
from windows!

Cleanup the management of names and use standard routines where possible.
Flag places where bonding device still doesn't work right with network
namespaces.

Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>
Signed-off-by: David S. Miller <davem@davemloft.net>