Bluetooth: Add timer for automatically disabling the service cache

We do not want the service cache to be enabled indefinitely after
mgmt_read_info is called. To solve this a timer is added which will
automatically disable the cache if mgmt_set_dev_class isn't called
within 5 seconds of calling mgmt_read_info.

Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>
Acked-by: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: Gustavo F. Padovan <padovan@profusion.mobi>