Use up-to-date name and version for the Docker Python API package.

docker-py appears to be an abandoned copy of the docker pypi package
stuck at 1.10.6. An issue with the script on Xenial prompted us to
update the dependency.

modules/profile/manifests/jenkins/agent.pp

@@ -71,7 +71,7 @@
     ensure => 'installed',
   }
 
-  # required by subprocess reaper script
+  # required by subprocess reaper and docker cleanup scripts
   package { 'python3-psutil':
     ensure => 'installed',
   }
@@ -100,9 +100,9 @@
   include docker
 
   # required by cleanup_docker script
-  python::pip { 'docker-py':
-    pkgname        => 'docker-py',
-    #ensure        => present, # defaults to present
+  python::pip { 'docker':
+    ensure  => '2.5.0',
+    pkgname => 'docker',
   }
 
   # script to clean up docker images from oldest