playbook: increase net.ipv6.route.max_size sysctl

This is needed specially for kernel after 4.16 (especially 4.19, kernel
version of Debian 10) because much more objects are counted in this
max_size limit.

See interesting discussion here: https://lore.kernel.org/patchwork/patch/1245043/

playbook/roles/vifib-server/tasks/main.yml

@@ -25,6 +25,7 @@
   - sysctl: name="net.ipv6.conf.default.accept_ra" value=0 sysctl_set=yes state=present reload=yes
   - sysctl: name="net.ipv6.conf.all.forwarding" value=1 sysctl_set=yes state=present reload=yes
   - sysctl: name="net.ipv6.conf.default.forwarding" value=1 sysctl_set=yes state=present reload=yes
+  - sysctl: name="net.ipv6.route.max_size" value=262144 sysctl_set=yes state=present reload=yes
 
   - include: kvm.yml
   - include: shuttle-modprobe.yml