utils: print from other thread appropriately
utils: print from other thread appropriately

in Flask, current_app is a werkzeug LocalProxy which uses thread (or
greenlet) local storage. Since async_genkey runs in another thread it's
invalid to call it in this manner.

ehartsuyker/securedrop,heartsucker/securedrop,ehartsuyker/securedrop,heartsucker/securedrop,heartsucker/securedrop,garrettr/securedrop,garrettr/securedrop,ehartsuyker/securedrop,garrettr/securedrop,garrettr/securedrop,conorsch/securedrop,ehartsuyker/securedrop,conorsch/securedrop,heartsucker/securedrop,conorsch/securedrop,ehartsuyker/securedrop,ehartsuyker/securedrop,conorsch/securedrop,heartsucker/securedrop,conorsch/securedrop