Fix from_fabric_wwn for qla2xxx

Closes #23

Reported-by: bsyd
Signed-off-by: Andy Grover <agrover@redhat.com>
Distinguish between qla2xxx and fcoe in wwns()

Use symbolic_name to distinguish between the two types of fcoe, handled
by different fabrics. This prevents both fabrics being shown in targetcli
if only one is present, and autocompletion of WWNs will only show the
proper WWNs for the fabric, if both are present.

Signed-off-by: Andy Grover <agrover@redhat.com>