[PATCH] docker: Update to Ubuntu 18.04 LTS

[Joel Stanley]

Ubuntu 17.10 was end of life in July. Update to the latest LTS.

Signed-off-by: Joel Stanley <joel at jms.id.au>
---
I ran this through travis last night and it passed on both ppc64le and
amd64 builders. I don't have an arm64 machine to test that architecture.

 docker/builder-include | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/docker/builder-include b/docker/builder-include
index 585be2656df6..783f0101dbd2 100644
--- a/docker/builder-include
+++ b/docker/builder-include
@@ -23,9 +23,9 @@ docker_from() {
 	local a="$(arch)"
 
 	case "${a}" in
-		amd64) echo "ubuntu:17.10" ;;
-		arm64) echo "arm64v8/ubuntu:17.10" ;;
-		ppc64le) echo "ppc64le/ubuntu:17.10" ;;
+		amd64) echo "ubuntu:18.04" ;;
+		arm64) echo "arm64v8/ubuntu:18.04" ;;
+		ppc64le) echo "ppc64le/ubuntu:18.04" ;;
 		*)
 			echo "${name}: ERROR: Unknown arch ${a}" >&2
 			exit 1
-- 
2.17.1