add nc checks to agent (Azure#2221)

parts/k8s/kubernetesagentcustomdata.yml

@@ -168,8 +168,8 @@ runcmd:
 - echo `date`,`hostname`, startruncmd>>/opt/m
 # the first arg is the number of retries, the second arg is the wait duration between two retries and the rest of the args are the cmd to run
 - retrycmd_if_failure() { retries=$1; wait=$2; shift && shift; for i in $(seq 1 $retries); do ${@}; [ $? -eq 0  ] && break || sleep $wait; done; echo Executed \"$@\" $i times; }
-- retrycmd_if_failure 120 1 nc -zw1 $(grep nameserver /etc/resolv.conf | cut -d \  -f 2) 53
-- retrycmd_if_failure 120 1 nc -zw1 azure.com 443
+- retrycmd_if_failure 120 1 nc -zuw1 $(grep nameserver /etc/resolv.conf | cut -d \  -f 2) 53
+- retrycmd_if_failure 120 1 nc -zw1 aptdocker.azureedge.net 443
 - apt-mark hold walinuxagent{{GetKubernetesAgentPreprovisionYaml .}}
 - echo `date`,`hostname`, preaptupdate>>/opt/m
 - retrycmd_if_failure 5 10 apt-get update