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
_logger.info('Worker (%d) CPU time limit (%s) reached.', self.pid, config['limit_time_cpu'])
            
            raise Exception('CPU time limit exceeded.')
        signal.signal(signal.SIGXCPU, time_expired)
        soft, hard = resource.getrlimit(resource.RLIMIT_CPU)
        resource.setrlimit(resource.RLIMIT_CPU, (cpu_time + config['limit_time_cpu'], hard))
    def process_work(self):
        pass
    def start(self):
        self.pid = os.getpid()
        self.setproctitle()
        _logger.info("Worker %s (%s) alive", self.__class__.__name__, self.pid)
        
        random.seed()
        if self.multi.socket:
            
            flags = fcntl.fcntl(self.multi.socket, fcntl.F_GETFD) | fcntl.FD_CLOEXEC
            fcntl.fcntl(self.multi.socket, fcntl.F_SETFD, flags)
            
            self.multi.socket.setblocking(0)
        signal.signal(signal.SIGINT, self.signal_handler)
        signal.signal(signal.SIGTERM, signal.SIG_DFL)
        signal.signal(signal.SIGCHLD, signal.SIG_DFL)
    def stop(self):