[mixer-e2e-test] add retry to prometheus query in check cache test (#12680)
[mixer-e2e-test] add retry to prometheus query in check cache test (#12680)

* check cache test sleep longer

* use retry instead of longer waiting

* reword error message

smawson/istio,smawson/istio,istio/istio,geeknoid/istio,smawson/istio,geeknoid/istio,geeknoid/istio,istio/istio,smawson/istio,istio/istio,smawson/istio,smawson/istio,geeknoid/istio,geeknoid/istio,istio/istio,istio/istio,geeknoid/istio