write vrouter-agent log to file

closes-jira-bug: CEM-22496
Change-Id: Ibc6f02a178fd92b7ba31121e658fed38cc6cd048

Author: Andrey-mp

containers/vrouter/agent/entrypoint.sh

@@ -1,4 +1,14 @@
 #!/bin/bash
+
+# save container output to log
+log_dir=${CONTAINER_LOG_DIR:-${LOG_DIR:-'/var/log/contrail'}/${NODE_TYPE}-${SERVICE_NAME}}
+mkdir -p $log_dir
+log_file="$log_dir/vrouter-agent-entrypoint.log"
+touch "$log_file"
+exec &> >(tee -a "$log_file")
+chmod 600 $log_file
+echo "INFO: =================== $(date) ==================="
+
 source /actions.sh
 
 echo "INFO: agent started in $AGENT_MODE mode"