Include voter initialization in officing voters lock

For reasons that might or might not affect production installations, the
test checking simultaneous requests to create poll voters in the
officing voters controller wasn't behaving as expected.

The expected behavior, since commit 9a8bfac5b, is that the second
request reaching the `with_lock` part of the code waits for the first
request to finish and so this second request raises an
`ActiveRecord::RecordInvalid` exception when trying to save a voter with
the same poll and the same user as the first one.

However, 95% of the time that wasn't the case. Instead, when entering
the `@user.with_lock` block, the second request would replace its
`@voter` object with the `@voter` object saved in the same request, so
the second call to `save!` would succeed as it would simply update the
existing record.

This is a behavior that we could accept if it were consistent and
happened 100% of the time, but that isn't the case. 5% of the time, we
do get the `ActiveRecord::RecordInvalid` exception. So 5% of the time we
got a failure in the test:

```
  1) Officing::VotersController POST create does not create two records
     with two simultaneous requests
     Failure/Error: @user.with_lock { @voter.save! }

     ActiveRecord::RecordInvalid:
       Validation failed: User User has already voted
     # ./app/controllers/officing/voters_controller.rb:25:in `block in create'
     # ./app/controllers/officing/voters_controller.rb:25:in `create'
     # ./app/controllers/application_controller.rb:50:in `switch_locale'
     # ./spec/controllers/officing/voters_controller_spec.rb:15:in `block (5 levels) in <top (required)>'
```

So we're changing the `with_lock` block so it includes the
initialization of the object. This way, we get the
`ActiveRecord::RecordInvalid` exception 100% of the time.

Note that in commit 9a8bfac5b we also rescued the
`ActionDispatch::IllegalStateError` exceptions. I'm not why we were
getting those exceptions when running the tests, and I'm not sure
whether we keep getting after these changes, but it doesn't really
matter. The reason is that in Consul Democracy 2.3.0 we're going to add
a unique index to the `poll_voters` table, which (according to the tests
done in the past) will make both the `@user.lock` block and rescuing the
`ActionDispatch::IllegalStateError` unnecessary.

So, in other words, these changes will never make it to production
because this part of the code will be changed again before releasing
version 2.3.0.

app/controllers/officing/voters_controller.rb

@@ -13,16 +13,19 @@ class Officing::VotersController < Officing::BaseController
   def create
     @poll = Poll.find(voter_params[:poll_id])
     @user = User.find(voter_params[:user_id])
-    @voter = Poll::Voter.new(document_type: @user.document_type,
-                             document_number: @user.document_number,
-                             user: @user,
-                             poll: @poll,
-                             origin: "booth",
-                             officer: current_user.poll_officer,
-                             booth_assignment: current_booth.booth_assignments.find_by(poll: @poll),
-                             officer_assignment: officer_assignment(@poll))
 
-    @user.with_lock { @voter.save! }
+    @user.with_lock do
+      @voter = Poll::Voter.new(document_type: @user.document_type,
+                               document_number: @user.document_number,
+                               user: @user,
+                               poll: @poll,
+                               origin: "booth",
+                               officer: current_user.poll_officer,
+                               booth_assignment: current_booth.booth_assignments.find_by(poll: @poll),
+                               officer_assignment: officer_assignment(@poll))
+
+      @voter.save!
+    end
   end
 
   private

spec/controllers/officing/voters_controller_spec.rb

@@ -15,7 +15,7 @@ describe Officing::VotersController do
             voter: { poll_id: poll.id, user_id: user.id },
             format: :js
           }
-        rescue ActionDispatch::IllegalStateError
+        rescue ActionDispatch::IllegalStateError, ActiveRecord::RecordInvalid
         end
       end.each(&:join)