envoy: Fail out on error generating protobufs
envoy: Fail out on error generating protobufs

The `for` statement is interpreted as a bash script by the make, so then
it executes every command in the bash without exiting on failure. Fix
this by running `set -e` first.

Signed-off-by: Joe Stringer <16a9a54ddf4259952e3c118c763138e83693d7fd@covalent.io>

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