[stream-refactor] allow doas_test to succeed on CentOS

Unlike on Debian, some environment variables that tickle
getpass.getuser() are being inherited. So use getuid() instead.

Also install the doas binary on CentOS. CI was changed (I believe) to
shrink the configuration matrix, and now these tests run on CentOS too.

tests/doas_test.py

@@ -1,5 +1,4 @@
 
-import getpass
 import os
 
 import mitogen
@@ -59,7 +58,7 @@ class DoasTest(testlib.DockerMixin, testlib.TestCase):
             password='has_sudo_password',
         )
         context = self.router.su(via=ssh, password='rootpassword')
-        self.assertEquals('root', context.call(getpass.getuser))
+        self.assertEquals(0, context.call(os.getuid))
 
 
 if __name__ == '__main__':

tests/image_prep/README.md

@@ -11,10 +11,13 @@ code, the OS X config just has the user accounts.
 See ../README.md for a (mostly) description of the accounts created.
 
 
+
 ## Building the containers
 
 ``./build_docker_images.sh``
 
+Requires Ansible 2.3.x.x in order to target CentOS 5
+
 
 ## Preparing an OS X box
 

tests/image_prep/_container_setup.yml

@@ -87,27 +87,24 @@
       shell: locale-gen
       when: distro == "Debian"
 
-    - name: Install prebuilt 'doas' binary on Debian
+    - name: Install prebuilt 'doas' binary
       unarchive:
         dest: /
         src: ../data/docker/doas-debian.tar.gz
-      when: distro == "Debian"
 
-    - name: Make prebuilt 'doas' binary executable on Debian
+    - name: Make prebuilt 'doas' binary executable
       file:
         path: /usr/local/bin/doas
         mode: 'u=rwxs,go=rx'
         owner: root
         group: root
-      when: distro == "Debian"
 
-    - name: Install doas.conf on Debian
+    - name: Install doas.conf
       copy:
         dest: /etc/doas.conf
         content: |
           permit :mitogen__group
           permit :root
-      when: distro == "Debian"
 
     - name: Vanilla Ansible needs simplejson on CentOS 5.
       shell: mkdir -p /usr/lib/python2.4/site-packages/simplejson/