[lucid] ubuntuone-preferences always shows plan as Free if it is not 50G

[Roman Yepishev]

STR:

1. Get a 20Gb subscription
2. Run ubuntuone-preferences in lucid
3. Look at current plan

Expected results: Paid plan (w/ mentioning 20Gb somewhere probably)

Current results: Free

Reason:
/usr/bin/ubuntuone-preferences:
        # assumes all paid accounts will have more than 50GB
        is_paid_account = total >= 50<<30
        self.plan_label.set_label(_("Paid") if is_paid_account else _("Free"))