Replace kernel-ml packages with kernel-lt

kernel-lt works better to resolve OVS support than kernel-ml.

dont merge untill packages are added to the mirror

Change-Id: I52403751cf8166a0ef6d00a1b1254b3068d82eaa
Related-bug: 1282493
Related-bug: 1263072
Fix typo for test group

Change-Id: Icecf79aaa54852561292364102e7a49fe4ec5344
Merge "Replace kernel-ml packages with kernel-lt"
Add workaround for kernel-lt-firmware

Change-Id: Iaf0a03a2310d76d66b8e52203187d3d4f68b1f1a
Merge "Add workaround for kernel-lt-firmware"
use stable/4.1 branches to build 4.1 images

Change-Id: I344f747b3ce85f697b8add8e02e0126b28ca86fc
Ceph build tweaks. Do not merge.

Change-Id: If7f369078f5e1b559a2ec2aa9429f3759e037ba4