Make sure Puma has restarted properly

We were getting an error when restarting Puma after upgrading Ruby. Even
if the restart command was sent successfully, Puma silently crashed and
the log had the following error:

/home/deploy/.rvm/rubies/ruby-2.4.9/lib/ruby/site_ruby/2.4.0/bundler/spec_set.rb:91:in
`block in materialize': Could not find rake-13.0.1 in any of the sources
(Bundler::GemNotFound)

So it looks like the crash happens because Puma was started when the
application used Ruby 2.4 and now when it's restarted it still tries to
use Ruby 2.4, even if the application now uses Ruby 2.5.

I haven't found a proper way to configure Puma so we can avoid this, so
as a workaround I've added the `puma:start` task after restarting Puma.
If Puma was successfully restarted, `puma:start` will do nothing; if
Puma crashed, `puma:start` will start it.

To guarantee the tasks will be executed in the proper order, the tasks
introduced by capistrano3-delayed_job and capistrano3-puma are cleared,
and then we configure the order so first we restart Puma, then restart
the Delayed Jobs processes (so there's enough time for Puma to crash if
Ruby was upgraded) and then start Puma.

config/deploy.rb

@@ -45,6 +45,9 @@ set(:config_files, %w[
 set :whenever_roles, -> { :app }
 
 namespace :deploy do
+  Rake::Task["delayed_job:default"].clear_actions
+  Rake::Task["puma:smart_restart"].clear_actions
+
   after :updating, "rvm1:install:rvm"
   after :updating, "rvm1:install:ruby"
   after :updating, "install_bundler_gem"
@@ -54,8 +57,9 @@ namespace :deploy do
   after  :publishing, "setup_puma"
 
   after :published, "deploy:restart"
-  before "deploy:restart", "puma:smart_restart"
+  before "deploy:restart", "puma:restart"
   before "deploy:restart", "delayed_job:restart"
+  before "deploy:restart", "puma:start"
 
   after :finished, "refresh_sitemap"