Impacted versions: 9, 10

Steps to reproduce:

1. Install mass_mailing.
2. Install an additional language (i.e. Spanish).
3. Log in as demo user.
4. Create a new partner, set its country to be "Spain".
4. Change demo user's lang to Spanish.
5. Create a new mass mailing.
5. Choose customer recipients.
5. Select those customers whose country is "España".
4. Design the email.
3. Send it.

Current behavior:
The demo user sees 1 record selected, the admin user sees 0 records. This happens because admin's lang is English and no countries are found if you search for "España" under that context.
Since the queue is sent under the admin user context, no mails are sent.
Demo user scratches his head (in case he ever notices no mails were sent).

Expected behavior:
Queue should be run under the same language as the one in the context when the user pressed the "send" button, to avoid losing records when some domain is applied over translated fields.

@Tecnativa
self.env.cr.execute("""
            SELECT COUNT(DISTINCT(stats.id)) AS nb_mails, COUNT(DISTINCT(clicks.mail_stat_id)) AS nb_clicks, stats.mass_mailing_campaign_id AS id
            FROM mail_mail_statistics AS stats
            LEFT OUTER JOIN link_tracker_click AS clicks ON clicks.mail_stat_id = stats.id
            WHERE stats.mass_mailing_campaign_id IN %s
            GROUP BY stats.mass_mailing_campaign_id
        """, (tuple(self.ids), ))
        campaign_data = self.env.cr.dictfetchall()
        mapped_data = dict([(c['id'], 100 * c['nb_clicks'] / c['nb_mails']) for c in campaign_data])
        for campaign in self:
            campaign.clicks_ratio = mapped_data.get(campaign.id, 0)
    def _compute_statistics(self):
        """ Compute statistics of the mass mailing campaign """
        self.env.cr.execute("""
            SELECT
                c.id as campaign_id,
                COUNT(s.id) AS total,
                COUNT(CASE WHEN s.sent is not null THEN 1 ELSE null END) AS sent,
                COUNT(CASE WHEN s.scheduled is not null AND s.sent is null AND s.exception is null THEN 1 ELSE null END) AS scheduled,
                COUNT(CASE WHEN s.scheduled is not null AND s.sent is null AND s.exception is not null THEN 1 ELSE null END) AS failed,