[scripts] Use master branch of beat.core to pull docker-pull script

scripts/before_build.sh

@@ -18,6 +18,6 @@ run_cmd buildout
 destdir="$(cd "$( dirname "${BASH_SOURCE[0]}" )" >/dev/null && pwd)"
 check_env destdir
 
-run_cmd curl -o ${destdir}/_core_docker_pull.sh --silent "https://gitlab.idiap.ch/beat/beat.core/raw/1.7.x/scripts/docker_pull.sh"
+run_cmd curl -o ${destdir}/_core_docker_pull.sh --silent "https://gitlab.idiap.ch/beat/beat.core/raw/master/scripts/docker_pull.sh"
 run_cmd chmod 755 ${destdir}/_core_docker_pull.sh
 run_cmd ${destdir}/_core_docker_pull.sh