node.xml: fix postfix mydestionation config

tripwire did not work because it send message at root@localhost
with this fix postfix accept also those destination

Reported-by: Brian McAllister <mcallister@mit.edu>
http://marc.info/?l=npaci-rocks-discussion&m=140666237216874&w=2
node.xml: fix database creation problem

the table aliases now has a foreign key on the nodes table, so it
should be defined after the nodes table
tests: add a test for the database schema creation