test: Enable Prometheus metrics in K8sHubbleTest
test: Enable Prometheus metrics in K8sHubbleTest

For now the test is pretty basic, just send curl to /metrics and
look for some metrics that are supposed to be there.

Fixes: #11498

Signed-off-by: Michi Mutsuzaki <a75494f12f73453b2bd75573f87b8f21fcc50565@isovalent.com>

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