Fix example 'Creation of two VTI Devices'

Kernel refuses to add tunnel 'ipsec0', because it has the same local and
remote as 'vti0'.
This also matches what is written in 'Connection-specific VTI Devices':

 "The kernel rejects the creation of a VTI device if the remote and local
  addresses are already in use by another VTI device."

Closes #25

docs/modules/ROOT/pages/features/routeBasedVpn.adoc

@@ -294,7 +294,7 @@ All of this also works for IPv6.
 ==== Example: Creation of two VTI Devices (vti0 and ipsec0)
 ----
 ip tunnel add vti0   local 192.168.0.1 remote 192.168.0.2 mode vti key 42
-ip tunnel add ipsec0 local 192.168.0.1 remote 192.168.0.2 mode vti key 0x01000201
+ip tunnel add ipsec0 local 192.168.0.1 remote 192.168.0.3 mode vti key 0x01000201
 sysctl -w net.ipv4.conf.vti0.disable_policy=1
 ip link set vti0 up
 ip route add 10.1.0.0/16 dev vti0