[FIX] module.loading: ensure installed modules are all loaded before installing new...

[FIX] module.loading: ensure installed modules are all loaded before installing new ones

After the recent change to make module install
atomically (code *and* data), we ran into issues
when installing a new module indirectly triggers
code of a not-yet-loaded-but-installed module,
via its data that is already in the database
(e.g. worflows or reports modified by this module
within another module, that now refer to its
code).
To avoid this, we now make sure that we only
install new modules on top of a consistent system
(code *and* data), by loading all installed or
'to upgrade' modules *before* starting to install
new ones.

lp bug: https://launchpad.net/bugs/809168 fixed

bzr revid: odo@openerp.com-20110712133343-unf610k23fa6d3pk