ci: Auto deploy latest build of master

After building and publishing a new "latest" container image, we can
automatically deploy it to production by restarting the *sshca*
Deployment.  We use `curl` here to patch the Deployment manually, since
`kubectl` is not available in the container image.  This is a simple
enough operation that it's not worth the effort of trying to install it.

ci/Jenkinsfile

@@ -40,6 +40,15 @@ pipeline {
                                 }
                             }
                         }
+
+                        stage('Deploy') {
+                            when {
+                                branch 'master'
+                            }
+                            steps {
+                                sh '. ci/deploy.sh'
+                            }
+                        }
                     }
                 }
             }