test/helpers: add GetEndpointMutableConfigurationOption function
test/helpers: add GetEndpointMutableConfigurationOption function

Add helper function which gets the value of a configuration option for a specific endpoint.

Signed-off by: Ian Vernon <ian@cilium.io>

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