update-osmo-ci-slaves: Fail jenkins jobs on script failure

It's been noted that jenkins job update-osmo-ci-on-slaves succeeds even
if make script called by some children function fails:

"""
../make/Makefile:57: recipe for target 'docker-build' failed
make: *** [docker-build] Terminated
make: Leaving directory '/home/osmocom-build/osmo-ci/_docker_playground/debian-stretch-jenkins'
+ exit 1
Finished: SUCCESS
"""

Change-Id: Iab9bc49eebee0f42657ff3ab5ffaa10315446440

scripts/common.sh

@@ -153,6 +153,7 @@ docker_images_require() {
 
 	# Subshell: run docker_images_require from jenkins-common.sh, pass all arguments
 	(. ../jenkins-common.sh; docker_images_require "$@")
-
+	ret=$?
 	cd "$oldpwd"
+	return $ret
 }

scripts/osmo-ci-docker-rebuild.sh

@@ -1,4 +1,5 @@
 #!/bin/sh
+set -e -x
 cd "$(dirname "$0")/.."
 . scripts/common.sh
 docker_images_require \