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
""" Start the openerp http server and cron processor.
    """
    global server
    load_server_wide_modules()
    if openerp.evented:
        server = GeventServer(openerp.service.wsgi_server.application)
    elif config['workers']:
        server = PreforkServer(openerp.service.wsgi_server.application)
    else:
        server = ThreadedServer(openerp.service.wsgi_server.application)
    watcher = None
    if config['dev_mode']:
        if watchdog:
            watcher = FSWatcher()
            watcher.start()
        else:
            _logger.warning("'watchdog' module not installed. Code autoreload feature is disabled")
        server.app = DebuggedApplication(server.app, evalex=True)
    rc = server.run(preload, stop)
    
    if getattr(openerp, 'phoenix', False):
        if watcher:
            watcher.stop()
        _reexec()
    return rc if rc else 0
def restart():