bug fix: Don't display vlan interfaces while creating network bridge

vlan brigdes aren't supported at this time so those interfaces should not be
displayed while creating a network bridge
The supported interfaces for a bridge network are: bare nic, bonding or bridge
device.

Signed-off-by: Aline Manera <alinefm@br.ibm.com>
bug fix: Update openSUSE instructions in README file

python-ethtool package isn't in the default openSUSE repository.
To get it installed, the user first need to add the Systems Management repository.
So add those instructions to README file.

Signed-off-by: Aline Manera <alinefm@br.ibm.com>
Signed-off-by: ShaoHe Feng <shaohef@linux.vnet.ibm.com>