Journalist GUI: Move tag checkout and verification into method
Journalist GUI: Move tag checkout and verification into method

Separating out this method for testability

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