gluon-mesh-vpn-core: Add dependency for KERNEL_NET_ACT_POLICE

This is a fix for the broken ingress traffic-shaping in gluon v2018.2.2
and possibly earlier.

For ingress traffic shaping the kernel option NET_ACT_POLICE is needed.
Before this patch there was no dependency to this. Neither in
gluon_core, gluon-mesh-vpn-core nor in the package.

This patch adds this dependency.

[Matthias Schiffer: move dependency from GLUON_CORE to gluon-mesh-vpn-core]

Fixes #1790