add metadatas on each kraken response, and update jormun instance each time

At startup jormungandr don't load the configuration of a new instance
fast enougth, it can wait 10 second before each scan, and if there is
some dead instances we add another second for them.

with this patch a most one request will be done without the timezone set
Merge pull request #770 from kinnou02/update_instance_on_call

add metadatas on each kraken response, and update jormun instance each time