Impacted versions:
9.0, 10.0, 11.0 (Maybe 8.0)
I don't know if it is really an expected behaviour for odoo but I like to expose it

Steps to reproduce:

1. Open an ir.cron record and change it to:
 - interval: minutes
 - next execution date: now + 1 minute

2. Open the odoo server log

Note: I'm using workers=3 but I don't know if there is possible to reproduce it without workers.

Current behavior:

You will see for each cron execution the following output
```txt
...
2018-06-01 16:18:33,432 20686 INFO 333561-11-0-42aff9-all odoo.modules.registry: Invalidating all model caches after database signaling.
...
2018-06-01 16:17:21,527 20687 INFO 333561-11-0-42aff9-all odoo.modules.loading: loading 1 modules...
2018-06-01 16:17:21,535 20687 INFO 333561-11-0-42aff9-all odoo.modules.loading: 1 modules loaded in 0.01s, 0 queries
2018-06-01 16:17:21,594 20687 INFO 333561-11-0-42aff9-all odoo.modules.loading: loading 206 modules...
2018-06-01 16:17:21,718 20687 INFO 333561-11-0-42aff9-all odoo.modules.loading: 206 modules loaded in 0.12s, 0 queries
2018-06-01 16:17:21,989 20687 INFO 333561-11-0-42aff9-all odoo.modules.loading: Modules loaded.
```

Expected behavior:
 - Review if the method that run from the cron really requires a invalidate cache and delete all registries.
 - Disable "minutes" for cron interval because all cache are deleted then is not valid use them.

Video/Screenshot link (optional):

 - [![IMAGE ALT TEXT HERE](https://img.youtube.com/vi/Be4FIeQjgjk/0.jpg)](https://youtu.be/Be4FIeQjgjk)
openerp/service/server.py
""" Shutdown the WSGI server. Wait for non deamon threads.
        """
        _logger.info("Initiating shutdown")
        _logger.info("Hit CTRL-C again or send a second signal to force the shutdown.")
        if self.httpd:
            self.httpd.shutdown()
            self.close_socket(self.httpd.socket)
        
        
        
        me = threading.currentThread()
        _logger.debug('current thread: %r', me)
        for thread in threading.enumerate():
            _logger.debug('process %r (%r)', thread, thread.isDaemon())
            if thread != me and not thread.isDaemon() and thread.ident != self.main_thread_id:
                while thread.isAlive():
                    _logger.debug('join and sleep')
                    
                    
                    thread.join(0.05)
                    time.sleep(0.05)
        _logger.debug('--')
        openerp.modules.registry.RegistryManager.delete_all()
        logging.shutdown()
    def run(self, preload=None, stop=False):