mender: attempt to load keys when creating mender instance
mender: attempt to load keys when creating mender instance

Previously performed in as part of config load operation, move the
operation of loading keys to mender setup handler.

Signed-off-by: Maciej Borzecki <f609d9f713abcd5f8f0e51f08dc151638a7681e7@open-rnd.pl>

bboozzoo/mender,bboozzoo/mender