[FIX] base: Failing test ``test_xmlrpc`` should be run at post-install time.


Test ``test_xmlrpc`` won't pass if you first install base:

    createdb -O openerp testing
    oe -i base -d testing --stop-after-init
    oe -d testing --update=all --test-enable --stop-after-init

Why:

Since ``auth_crypt`` is now installed by default, ``test_xmlrpc`` would not pass
on a pre-installed base because ``auth_crypt`` would not be loaded to handle
login before base's tests would be run. So force to wait all modules to
be loaded before running ``test_xmlrpc``.

Why runbot is not spotting this:

Because test are run at install phase : ``test_xmlrpc`` is run before 
``auth_crypt`` was ever installed.