utils/async.py: bump default timeout to 10s
utils/async.py: bump default timeout to 10s

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