Use a new AWS client on each request

This was the cause of the radiator going offline.

This should stop us from hitting a limit imposed by the JDK due to a possibility of an Entity Expansion Attack...

http://blog.bdoughan.com/2011/03/preventing-entity-expansion-attacks-in.html

@janua take a look and see if this makes sense for the front tool too (and implement there if it does).