Try another container if starting an rds shell fails

[snim2]

If we do want to merge this, then a bunch of other scripts need to be changed, similarly

[rjw1]

diff --git a/bin/rds/export-dump b/bin/rds/export-dump
index 542accb..63fcc08 100755
--- a/bin/rds/export-dump
+++ b/bin/rds/export-dump
@@ -108,8 +108,9 @@ then
       --filters "Name=vpc-id,Values=$RDS_VPC" "Name=instance-state-code,Values=16" Name=tag:Name,Values="$INFRASTRUCTURE_NAME-$ENVIRONMENT*"
   )
   ECS_INSTANCE_ID=$(
+  NUMBER_OF_INSTANCES=$(echo "$ECS_INSTANCES" | jq -r .Reservations | jq length)
     echo "$ECS_INSTANCES" \
-      | jq -r .Reservations[0].Instances[0].InstanceId
+      | jq --arg i $(($RANDOM % $NUMBER_OF_INSTANCES)) -r '.Reservations[$i|tonumber].Instances[0].InstanceId'
   )
 fi

is something ive been playign with.