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)
if config['xmlrpc']:
            while len(self.workers_http) < self.population:
                self.worker_spawn(WorkerHTTP, self.workers_http)
            if not self.long_polling_pid:
                self.long_polling_spawn()
        while len(self.workers_cron) < config['max_cron_threads']:
            self.worker_spawn(WorkerCron, self.workers_cron)
    def sleep(self):
        try:
            
            fds = dict([(w.watchdog_pipe[0], w) for k, w in self.workers.items()])
            fd_in = fds.keys() + [self.pipe[0]]
            
            ready = select.select(fd_in, [], [], self.beat)
            
            for fd in ready[0]:
                if fd in fds:
                    fds[fd].watchdog_time = time.time()
                try:
                    
                    while os.read(fd, 1):
                        pass
                except OSError, e:
                    if e.errno not in [errno.EAGAIN]:
                        raise
        except select.error, e:
            if e[0] not in [errno.EINTR]:
                raise
    def start(self):