Merge pull request #25 from cvubrugier/master

Make except clause compatible with Python 3 in scripts/targetcli
Make use of ethtool module optional

targetcli will now use the python-ethtool module if present to generate a
list of possible portal listening addresses, but will still work if it
is not present.

Signed-off-by: Andy Grover <agrover@redhat.com>
Do not use string.maketrans() since it does not exist in Python 3