labels: Whitelist "id." prefix by default
labels: Whitelist "id." prefix by default

So far, the label prefix "io.cilium" has been whitelisted by default.
Additionally whitelist "id.". This can be overwritten using the
--label-prefix-file option.

This allows the following construct to work out of the box:
  docker run -l id.frontend [....]
  docker run -l id.backend [...]

Signed-off-by: Thomas Graf <5f50a84c1fa3bcff146405017f36aec1a10a9e38@cilium.io>

tgraf/cilium,tgraf/cilium,tklauser/cilium,michi-covalent/cilium,scanf/cilium,scanf/cilium,tgraf/cilium,eloycoto/cilium,cilium/cilium,cilium/cilium,tklauser/cilium,eloycoto/cilium,michi-covalent/cilium,tklauser/cilium,mskarbek/cilium,mskarbek/cilium,eloycoto/cilium,scanf/cilium,eloycoto/cilium,michi-covalent/cilium,michi-covalent/cilium,cilium/cilium,gumpt/cilium,mskarbek/cilium,cilium-team/cilium,cilium/cilium,gumpt/cilium,tgraf/cilium,gumpt/cilium,scanf/cilium,scanf/cilium,tklauser/cilium,mskarbek/cilium,eloycoto/cilium,tgraf/cilium,gumpt/cilium,mskarbek/cilium,scanf/cilium,eloycoto/cilium,cilium-team/cilium,gumpt/cilium,mskarbek/cilium,gumpt/cilium,eloycoto/cilium,cilium/cilium,tgraf/cilium,gumpt/cilium,michi-covalent/cilium,tklauser/cilium,scanf/cilium