ci/docker: Run containers with --init

This should avoid a bunch of zombie processes.

Signed-off-by: Stewart Smith <stewart@linux.ibm.com>
diff --git a/ci/build.sh b/ci/build.sh
index 012aaef..f663ef4 100755
--- a/ci/build.sh
+++ b/ci/build.sh
@@ -70,7 +70,7 @@
 	else
 		BINDARG="--mount=type=bind,src=${PWD},dst=${PWD}"
 	fi
-	$DOCKER_PREFIX docker run --cap-add=sys_admin --net=host --rm=true \
+	$DOCKER_PREFIX docker run --init --cap-add=sys_admin --net=host --rm=true \
 	 --user="${USER}" -w "${PWD}" "${BINDARG}" \
          -t $1 $2
 }