ovs-monitor-ipsec: Allow exit of ipsec daemon maintaining state.

ovs-monitor-ipsec: Allow exit of ipsec daemon maintaining state.

When 'ovs-monitor-ipsec' exits, it clears all persistent state (i.e.
active ipsec connections, /etc/ipsec.conf, certs/keys). In some
use-cases, we may want to exit and maintain state so that ipsec
connectivity is maintained. One example of this is during an
upgrade. This will require the caller to clear this persistent
state when appropriate (e.g. before 'ovs-monitor-ipsec') is restarted.

Signed-off-by: Mark Gray <mark.d.gray@redhat.com>
Acked-by: Eelco Chaudron <echaudro@redhat.com>
Acked-by: Flavio Leitner <fbl@sysclose.org>
Signed-off-by: Ilya Maximets <i.maximets@ovn.org>