ipsec-tools: fix the reconnecting issue by delaying closing sockets.

When upper layers die first, the server might send messages to purge
IPSec sessions. If the sockets are closed before consuming these messages,
the server might keep sending for several minutes. The next run might be
failed because of these messages.

Ideally messages for the previous run should be dropped. However, the
server might think sessions are being renewed, so it sends updated
messages to purge them. This change tries to fix the issue by delaying
for few seconds before exiting.

Bug: 6376948
Change-Id: If735a7a202a2ac7763966e300936bc6e6ba4a53c
1 file changed