Use privilege escalation to attach to containers

When the play context contains 'become' for ansible privilege
escalation, apply the configured become method (sudo) to the command
used to attach to a container. This allows for non-root users to use the
connection plugin to connect to containers.

Closes-Bug: 1645732

Change-Id: I485bd0aa850f39201654c808f0c61d26113f6390

connection/ssh.py

@@ -425,6 +425,9 @@ class Connection(SSH.Connection):
                     SSH.shlex_quote(cmd)
                 )
 
+            if self._play_context.become:
+                cmd = ' '.join((self._play_context.become_method, cmd))
+
         elif self._chroot_check():
             chroot_command = 'chroot %s' % self.chroot_path
             cmd = '%s %s' % (chroot_command, cmd)

tests/host_vars/container1.yml

@@ -15,4 +15,3 @@
 
 ansible_host: 10.100.100.2
 ansible_become: True
-ansible_user: root

tests/test-connection-plugin.yml

@@ -16,7 +16,6 @@
 - name: Fail if sshd is running in the containers
   hosts: all_containers:alt_containers
   gather_facts: no
-  user: root
   become: True
   tasks:
     - name: Ensure sshd is not running
@@ -29,7 +28,6 @@
 - name: Test the connection plugin container awareness functions
   hosts: all_containers:alt_containers
   gather_facts: no
-  user: root
   become: True
   tasks:
     - name: Test container ping
@@ -40,7 +38,6 @@
 - name: Test delegation in the container aware connection plugin
   hosts: localhost
   gather_facts: no
-  user: root
   become: True
   tasks:
     - name: Test container delegation without templating
@@ -60,7 +57,6 @@
 - name: Test conditional delegation
   hosts: container1
   gather_facts: no
-  user: root
   become: True
   vars:
     delegate_control: "target-host"
@@ -76,7 +72,6 @@
 - name: Test delegation between container physical_hosts
   hosts: fakecontainer
   gather_facts: no
-  user: root
   become: True
   tasks:
     - name: Test delegation between containers on different hosts
@@ -86,6 +81,7 @@
 
 - name: Test container_user attribute
   hosts: container1
+  user: root
   tasks:
     - name: Ensure container alt user
       user: