backup.pl: Fixes bug13737 - restarts ipsec to use the restored certs etc

backup.pl: Fixes bug13737 - restarts ipsec to use the restored certs etc

- This adds a check if the ipsec server is enabled. If it is then ipsecctrl is run to
   restart ipsec and ensure that the restored certs are all being used.
- Tested this out on my vm testbed and confirmed that with this I could restore a backup
   and make the client connection as previously set up.
- Without this I had to press the Save button on the ipsec WUI page to get the certs
   etc being used.

Fixes: bug13737
Tested-by: Adolf Belka <adolf.belka@ipfire.org>
Signed-off-by: Adolf Belka <adolf.belka@ipfire.org>
Signed-off-by: Michael Tremer <michael.tremer@ipfire.org>