gitlab-runner exec docker does not execute global after_script and before_script properly

Summary

When the runner is used to test a configuration with exec docker, after_script is not executed if it has been defined in the global scope. before_script on the other hand works as expected if defined in the global scope, but not if inside a default: block.

Steps to reproduce

git clone git@gitlab.com:niosHD/mwe-gitlabci-paths.git
cd mwe-gitlabci-paths
gitlab-runner exec docker job1

Actual behavior

The global after_script commands are not executed.

Expected behavior

Globally defined after_script or one defined in default: is executed like on the official Gitlab CI runners and similarly like locally defined after_script is executed. (e.g., gitlab-runner exec docker job2)

Relevant logs and/or screenshots

Incorrect output where no after_script is executed:

Running with gitlab-ci-multi-runner 9.2.0 (adfc387)
  on  ()
Using Docker executor with image ubuntu:16.04 ...
Using docker image sha256:8fc3a7eccb276aae30ed9e67da418a69055f6f0bf047a501355ab09f79f427b5 for predefined container...
Pulling docker image ubuntu:16.04 ...
Using docker image ubuntu:16.04 ID=sha256:ebcd9d4fca80e9e8afc525d8a38e7c56825dfb4a220ed77156f9fb13b14d4ab7 for build container...
Running on runner--project-0-concurrent-0 via t440smw...
Cloning repository...
Cloning into '/builds/project-0'...
done.
Checking out 65899193 as master...
Skipping Git submodules setup
$ echo "global before_script"
global before_script
$ mkdir _build
$ cd _build
$ pwd
/builds/project-0/_build

$ echo "job1"
job1
$ pwd
/builds/project-0/_build
Running after script...
Job succeeded

Environment description

% docker info
Containers: 0
 Running: 0
 Paused: 0
 Stopped: 0
Images: 5
Server Version: 17.05.0-ce
Storage Driver: aufs
 Root Dir: /var/lib/docker/aufs
 Backing Filesystem: extfs
 Dirs: 10
 Dirperm1 Supported: true
Logging Driver: json-file
Cgroup Driver: cgroupfs
Plugins: 
 Volume: local
 Network: bridge host macvlan null overlay
Swarm: inactive
Runtimes: runc
Default Runtime: runc
Init Binary: docker-init
containerd version: 9048e5e50717ea4497b757314bad98ea3763c145
runc version: 9c2d8d184e5da67c95d601382adf14862e4f2228
init version: 949e6fa
Security Options:
 apparmor
 seccomp
  Profile: default
Kernel Version: 4.4.0-78-generic
Operating System: Ubuntu 16.04.2 LTS
OSType: linux
Architecture: x86_64
CPUs: 4
Total Memory: 11.45GiB
Name: xxxxxx
ID: xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Docker Root Dir: /var/lib/docker
Debug Mode (client): false
Debug Mode (server): false
Registry: https://index.docker.io/v1/
Experimental: false
Insecure Registries:
 127.0.0.0/8
Live Restore Enabled: false

WARNING: No swap limit support

Used GitLab Runner version

% gitlab-runner -v                                                                                                                                                                                   
Version:      9.2.0
Git revision: adfc387
Git branch:   9-2-stable
GO version:   go1.7.5
Built:        Mon, 22 May 2017 16:00:24 +0000
OS/Arch:      linux/amd64