CI: Run netperf test on master
CI: Run netperf test on master

The current conditional was incorrent because the `branch` only can be
used on multibranch jobs. With the current job configuration the
validation need to happens using the ENV variables.

Signed-off-by: Eloy Coto <2a8acc28452926ceac4d9db555411743254cf5f9@gmail.com>

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