Add proxy retry details to SSM

We jointly debugged a situation where the IP address of the ALB seemed to swap out and apache2 wasn't happy (most likely cached the old IP).  We think this may prevent old IPs from being cached and failing.

terraform-unity/ssm.tf

@@ -22,7 +22,7 @@ resource "aws_ssm_parameter" "managementproxy_config" {
   value      = <<-EOT
 
     <Location "/${var.project}/${var.venue}/management/">
-        ProxyPass "http://${var.mgmt_dns}/" upgrade=websocket
+        ProxyPass "http://${var.mgmt_dns}/" upgrade=websocket retry=5 disablereuse=On
         ProxyPassReverse "http://${var.mgmt_dns}/"
         ProxyPreserveHost On
         FallbackResource /management/index.html