test/extended/networking: fix [pod sysctls should not affect node] to use known host interfaces
test/extended/networking: fix [pod sysctls should not affect node] to use known host interfaces

This test was listing all interfaces on the host with 'ls /sys/class/net'
which does not return a stable order of interfaces. Thus it was sometimes
reading host-side veths of pods, which would be gone (because we run
tests in parallel and pods are starting/stopping all the time) by the time
the test wanted to read the interface's sysctls.

Jun  2 16:13:38.827: INFO: Error running /usr/bin/oc --namespace=e2e-test-tuning-vz9kr --kubeconfig=/tmp/secret/kubeconfig exec nodeaccess-pod-lmbdb -- cat /host/proc/sys/net/ipv4/conf/090399bc34a8bcf/send_redirects:
StdOut>
cat: can't open '/host/proc/sys/net/ipv4/conf/090399bc34a8bcf/send_redirects': No such file or directory
command terminated with exit code 1
StdErr>
cat: can't open '/host/proc/sys/net/ipv4/conf/090399bc34a8bcf/send_redirects': No such file or directory
command terminated with exit code 1

Instead of grabbing random interfaces from the host that may or may not
exist when the rest of the test runs, make the test own all the interfaces
it uses by creating it's own host interface via a second Network Attachment
Definition.

It gets worse... CreateExecPodOrFail() doesn't return the pod that was actually
created, it just returns the template it passed ot Create(). So the
nodeaccess pod's Spec.NodeName is empty, which was copied to the other
test pods, meaning they probably aren't even scheduled to the same node
and wouldn't be testing the same host interfaces. Fix that.

hroyrh/origin,csrwng/origin,akram/origin,mahak/origin,bparees/origin,hroyrh/origin,csrwng/origin,mahak/origin,soltysh/origin,csrwng/origin,deads2k/origin,mfojtik/origin,mfojtik/origin,hroyrh/origin,openshift/origin,jsafrane/origin,bparees/origin,jsafrane/origin,akram/origin,jsafrane/origin,deads2k/origin,openshift/origin,mahak/origin,bparees/origin,akram/origin,deads2k/origin,mfojtik/origin,soltysh/origin,openshift/origin,soltysh/origin