vpnmain.cgi: Change the log name from "ipsec" to "charon"

vpnmain.cgi: Change the log name from "ipsec" to "charon"

- The use of "ipsec" currently means that none of these messages are shown in the
   system log with IPSec selected as that is looking for charon.
- This patch changes all "ipsec" entries in this file to "charon"
- This results in the log messages for generation and regeneration of the root/host
   certificate set being shown in the system log. Without this then the messages log
   has to be searched from the command line with grep.
- Tested out on a physical IPFire system.

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>