Comment 2 for bug 1524093

FYI if anyone is also affected by this bug, I was able to find a workaround. See the last comment by idallen here:

http://ubuntuforums.org/showthread.php?t=1431860&p=12313662#post12313662

Essentially you want to do this:

* Remove all references to interfaces from the /etc/dhcp/dhclient.conf file
* Create separate configuration files for each interface with the options specific to each interface
* In the /etc/network/interfaces file, mark all DHCP interfaces as "manual" instead of "dhcp"
* Add a line to /etc/network/interfaces for each DHCP interface to manually bring it up using a command line that explicitly specifies its config file

For example, this is one of the stanzas in my /e/n/i file:

allow-hotplug lte0
iface lte0 inet manual
up dhclient -1 -v -cf /etc/dhcp/dhclient-lte0.conf -pf /run/dhclient.lte0.pid -lf /var/lib/dhcp/dhclient.lte0.leases lte0
down dhclient -r -cf /etc/dhcp/dhclient-lte0.conf -lf /var/lib/dhcp/dhclient.lte0.leases lte0