cubicweb-dataio #3479711 Use lgdb list_tables [open]

In the MassiveObjectStore we get all the tables using:

cu = self.session.system_sql('SELECT tablename FROM pg_tables WHERE schemaname=%(s)s', {'s': self.pg_schema})

We should use lgdb list_tables function.

prioritynormal
typebug
done in<not specified>
load0.200
load left0.200
closed by<not specified>