base/ubuntu: use 'ussuri' packages from UCA

Change-Id: Ia977d60e170efc1d4567bcea7f318b9d87233458

docker/base/sources.list.ubuntu

@@ -10,7 +10,7 @@ deb http://archive.ubuntu.com/ubuntu/ bionic-backports main universe
 
 # We need to add the repo for the updated packages they provide. The main ones
 # are qemu, libvirt, and openvswitch.
-deb http://ubuntu-cloud.archive.canonical.com/ubuntu bionic-updates/train main
+deb http://ubuntu-cloud.archive.canonical.com/ubuntu bionic-updates/ussuri main
 
 # NOTE(hrw): repositories below are added into image when they are needed as
 # separate files in /etc/apt/sources.list.d/ directory. For that purpose they

docker/base/sources.list.ubuntu.aarch64

@@ -8,7 +8,7 @@ deb http://ports.ubuntu.com/ bionic-backports main universe
 
 # We need to add the repo for the updated packages they provide. The main ones
 # are qemu, libvirt, and openvswitch.
-deb http://ubuntu-cloud.archive.canonical.com/ubuntu bionic-updates/train main
+deb http://ubuntu-cloud.archive.canonical.com/ubuntu bionic-updates/ussuri main
 
 # NOTE(hrw): repositories below are added into image when they are needed as
 # separate files in /etc/apt/sources.list.d/ directory. For that purpose they

docker/base/sources.list.ubuntu.ppc64le

@@ -8,7 +8,7 @@ deb http://ports.ubuntu.com/ bionic-backports main universe
 
 # We need to add the repo for the updated packages they provide. The main ones
 # are qemu, libvirt, and openvswitch.
-deb http://ubuntu-cloud.archive.canonical.com/ubuntu bionic-updates/train main
+deb http://ubuntu-cloud.archive.canonical.com/ubuntu bionic-updates/ussuri main
 
 # NOTE(hrw): repositories below are added into image when they are needed as
 # separate files in /etc/apt/sources.list.d/ directory. For that purpose they