cilium-docker: Refactor setup of container link device
cilium-docker: Refactor setup of container link device

- Refactor out common error handling bits.
- In the case of an error, do not try to remove link device if it
  hasn't been created. Otherwise, netlink.LinkDel will panic.

Signed-off-by: Martynas Pumputis <b14a8f953b021d09d1aafdca53cb27d7d9cede0c@covalent.io>

michi-covalent/cilium,michi-covalent/cilium,tklauser/cilium,cilium-team/cilium,tgraf/cilium,cilium/cilium,tklauser/cilium,michi-covalent/cilium,tklauser/cilium,cilium/cilium,tklauser/cilium,cilium/cilium,cilium/cilium,tgraf/cilium,tgraf/cilium,tgraf/cilium,cilium/cilium,cilium-team/cilium,tgraf/cilium,tgraf/cilium,michi-covalent/cilium,tklauser/cilium,michi-covalent/cilium