OpenVPN: Add start of static routes in client N2N

OpenVPN: Add start of static routes in client N2N

Fixes: #12529
- If a client N2N configuration will be imported into IPFire systems,
a line will be added which calls the --up script to restart the
static route initscript. Since this is IPFire specific, i will only be
added via import on IPFire system.
- Deleted unneeded line in CLIENTCONF section.
- Added description to SERVERCONF section.

Signed-off-by: ummeegge <erik.kapfer@ipfire.org>
Signed-off-by: Michael Tremer <michael.tremer@ipfire.org>