Fixes for e2e testing after Alpine bump

[ijc]

Somewhere between Thursday and Friday last week the docker:test-dind image was updated from an alpine 3.9.0 base to 3.9.2. This broke the use of chsh in e2e/testdata/Dockerfile.connhelper-ssh:

Step 1/6 : FROM docker:test-dind
test-dind: Pulling from library/docker
Digest: sha256:ec353956a21300964a7eb2b620a742c2730f618f4df35f60609b30969cd83ce8
Status: Downloaded newer image for docker:test-dind
 ---> 85e924caedbd
Step 2/6 : RUN apk --no-cache add shadow openssh-server &&   groupadd -f docker &&   useradd -m penguin &&   usermod -aG docker penguin &&   usermod -p $(head -c32 /dev/urandom | base64) penguin &&   chsh -s /bin/sh penguin &&   ssh-keygen -A
 ---> Running in 35e0398d93bd
fetch http://dl-cdn.alpinelinux.org/alpine/v3.9/main/x86_64/APKINDEX.tar.gz
fetch http://dl-cdn.alpinelinux.org/alpine/v3.9/community/x86_64/APKINDEX.tar.gz
(1/5) Installing openssh-keygen (7.9_p1-r4)
(2/5) Installing openssh-server-common (7.9_p1-r4)
(3/5) Installing openssh-server (7.9_p1-r4)
(4/5) Installing linux-pam (1.3.0-r0)
(5/5) Installing shadow (4.5-r0)
Executing busybox-1.29.3-r10.trigger
OK: 22 MiB in 44 packages
�[91mCreating mailbox file: No such file or directory
�[0m�[91mPassword: �[0m�[91mchsh: PAM: Authentication token manipulation error
�[0mService 'engine' failed to build: The command '/bin/sh -c apk --no-cache add shadow openssh-server &&   groupadd -f docker &&   useradd -m penguin &&   usermod -aG docker penguin &&   usermod -p $(head -c32 /dev/urandom | base64) penguin &&   chsh -s /bin/sh penguin &&   ssh-keygen -A' returned a non-zero code: 1
docker.Makefile:152: recipe for target 'test-e2e-connhelper-ssh' failed
make: *** [test-e2e-connhelper-ssh] Error 1

(this seems to relate to root's entry in /etc/shadow changing from root:::0:::::\nbin:!::0::::: to root:!::0:::::\nbin:!::0:::::).

Avoid this by just using the --shell option to useradd instead.

Also simplify things by using --password instead of usermod -p (even though this was not broken) and also spell out -m in full as --create-home for clarity.

[codecov-io]

Codecov Report

Merging #1728 into master will increase coverage by <.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #1728      +/-   ##
==========================================
+ Coverage   56.14%   56.14%   +<.01%     
==========================================
  Files         306      306              
  Lines       21031    21028       -3     
==========================================
  Hits        11807    11807              
+ Misses       8369     8366       -3     
  Partials      855      855

[thaJeztah]

LGTM

[thaJeztah]

we should probably cherry-pick this into the release-branch as well

[silvin-lubecki]

LGTM