EFI systems don't boot under maas in 2.1.3-proposed

MAAS Version:

2.1.3+bzr5571-0ubuntu1~16.04.1

What happened:

When I boot EFI systems through MAAS, they get stuck very early in the PXE process. Commission/enlist/deploy are all affected.

From some debugging with andres:

Basically, MAAS now sends ""cc:{'datasource_list': ['MAAS']}end_cc"" in the kernel command line to select the MAAS datasource to address issues where cloud-init reads cloud-config from localdisk first.

However, the following errors are shown. Note that this only happens when booting EFI/grub. Any ideas?

error: syntax error.
error: Incorrect command.
error: syntax error.
error: Incorrect command.
error: syntax error.
alloc magic is broken at 0x3ec88940: 0
Aborted. Press any key to exit.error: you need to load the kernel first.

I captured this terminal output from a *good* (non-efi) machine on 2.1.3, in case it's useful. The EFI machines (*broken*) I have all don't seem to show this when booting, so I can't give you what is shown for those.

PXELINUX 6.03 PXE 20151222 Copyright (C) 1994-2014 H. Peter Anvin et al
Booting under MAAS direction...
nomodeset iscsi_target_name=iqn.2004-05.com.ubuntu:maas:ephemeral-ubuntu-amd64-g
a-16.04-xenial-daily iscsi_target_ip=10.96.0.10 iscsi_target_port=3260 iscsi_ini
tiator=albany ip=::::albany:BOOTIF ip6=off ro root=/dev/disk/by-path/ip-10.96.0.
10:3260-iscsi-iqn.2004-05.com.ubuntu:maas:ephemeral-ubuntu-amd64-ga-16.04-xenial
-daily-lun-1 overlayroot=tmpfs cc:{'datasource_list': ['MAAS']}end_cc cloud-conf
ig-url=http://10.96.0.10/MAAS/metadata/latest/by-id/node-3934820a-546c-11e4-b3f2
-2c59e54ace74/?op=get_preseed log_host=10.96.0.10 log_port=514 --- console=ttyS1
 console=tty0
Loading ubuntu/amd64/ga-16.04/xenial/daily/boot-k...