[strongSwan] mixing ipv4 and ipv6 subnets does not work

[Niccolò Belli]

If I add the ipv6 subnet first I get:

# bad subnet: leftsubnet=a:b:c:0300::/56,1.2.3.4/28 [non-ipv6 address 
may not contain `:']
   bad argument value in conn 'linode-linuxsystems'
### 1 parsing error (0 fatal) ###

while if I add the ipv4 subnet first I get not errors but it doesn't 
tunnel the traffic toward 1.2.3.4/28

Niccolò