Updates to Docker

[laceysanderson]

This is a placeholder issue for some updates I would like to make to the dockerfile. Specifically,

• Ensure PostgreSQL is shut down properly after its install
• We no longer need to check to install phpspec/prophecy-phpunit -always install it

Also address these messages:

   - Installing composer/installers (v1.12.0): Extracting archive
composer/installers contains a Composer plugin which is blocked by your allow-plugins config. You may add it to the list if you consider it safe. See https://getcomposer.org/allow-plugins
You can run "composer config --no-plugins allow-plugins.composer/installers [true|false]" to enable it (true) or keep it disabled and suppress this warning (false)
  - Installing drupal/core-composer-scaffold (9.2.x-dev 3c9efe8): Extracting archive
drupal/core-composer-scaffold contains a Composer plugin which is blocked by your allow-plugins config. You may add it to the list if you consider it safe. See https://getcomposer.org/allow-plugins
You can run "composer config --no-plugins allow-plugins.drupal/core-composer-scaffold [true|false]" to enable it (true) or keep it disabled and suppress this warning (false)
  - Installing drupal/core-project-message (9.2.x-dev 812d6da): Extracting archive
drupal/core-project-message contains a Composer plugin which is blocked by your allow-plugins config. You may add it to the list if you consider it safe. See https://getcomposer.org/allow-plugins
You can run "composer config --no-plugins allow-plugins.drupal/core-project-message [true|false]" to enable it (true) or keep it disabled and suppress this warning (false)
composer/installers contains a Composer plugin which is blocked by your allow-plugins config. You may add it to the list if you consider it safe. See https://getcomposer.org/allow-plugins
You can run "composer config --no-plugins allow-plugins.composer/installers [true|false]" to enable it (true) or keep it disabled and suppress this warning (false)
drupal/core-composer-scaffold contains a Composer plugin which is blocked by your allow-plugins config. You may add it to the list if you consider it safe. See https://getcomposer.org/allow-plugins
You can run "composer config --no-plugins allow-plugins.drupal/core-composer-scaffold [true|false]" to enable it (true) or keep it disabled and suppress this warning (false)
drupal/core-project-message contains a Composer plugin which is blocked by your allow-plugins config. You may add it to the list if you consider it safe. See https://getcomposer.org/allow-plugins
You can run "composer config --no-plugins allow-plugins.drupal/core-project-message [true|false]" to enable it (true) or keep it disabled and suppress this warning (false)
  - Installing drupal/console-extend-plugin (0.9.5): Extracting archive
drupal/console-extend-plugin contains a Composer plugin which is blocked by your allow-plugins config. You may add it to the list if you consider it safe. See https://getcomposer.org/allow-plugins
You can run "composer config --no-plugins allow-plugins.drupal/console-extend-plugin [true|false]" to enable it (true) or keep it disabled and suppress this warning (false)