Comment 19 for bug 1693819

I should note:

1. The isc-dhcp code is common between dhcpd and dhclient
2. The current system interfaces are enumerated in common/discover.c, and that code - in next_iface() - strips the interface alias from all enumerated interfaces, so when dhcpd or dhclient is comparing a parameter against an existing interface, none of the existing enumerated interface names will have aliases
3. The interface parameters are parsed separately for dhcpd and dhclient; my patch changes *only* the parsing for dhclient, in client/dhclient.c, so that any command line interface names have their alias stripped
4. Other places that parse interface name parameters are dhcpd (in server/dhcpd.c), interface hotplug (maybe? in server/mdb.c, not sure about this file), and the dhcp relay (in relay/dhcrelay.c); my patch does *not* change any of these places, so interface name parameters to dhcpd, the dhcp relay, or in mdb.c, will still have interface aliases, and will not match any of the internally-enumerated (in common/discover.c) interface names. However, my patch narrowly fixes this specific bug, of 'dhclient -6 eth0:1' not working.