e2e: simplify check_adjacency helper

This commit simplifies the check_adjacency helper to us the curl_pod
helper rather than a re-written version of it. It also simplifies the
curl_pod helper slightly to avoid the need for an additional shell.
Signed-off-by: Lucas Servén Marín <lserven@gmail.com>

e2e/lib.sh

@@ -143,7 +143,7 @@ delete_cluster () {
 }
 
 curl_pod() {
-	_kubectl get pods -l app.kubernetes.io/name=curl -o name | xargs -I{} "$KUBECTL_BINARY" --kubeconfig="$KUBECONFIG" exec {} -- /bin/sh -c "curl $*"
+	_kubectl get pods -l app.kubernetes.io/name=curl -o name | xargs -I{} "$KUBECTL_BINARY" --kubeconfig="$KUBECONFIG" exec {} -- /usr/bin/curl "$@"
 }
 
 check_ping() {
@@ -174,7 +174,7 @@ check_ping() {
 }
 
 check_adjacent() {
-        _kubectl get pods -l app.kubernetes.io/name=curl -o name | xargs -I{} "$KUBECTL_BINARY" --kubeconfig="$KUBECONFIG" exec {} -- /bin/sh -c 'curl -m 1 -s adjacency:8080/?format=fancy'
+	curl_pod adjacency:8080/?format=fancy
 	[ "$(curl_pod -m 1 -s adjacency:8080/?format=json | jq '.[].latencies[].ok' | grep -c true)" -eq $(($1*$1)) ]
 }