fixes gpg check for test app key
fixes gpg check for test app key

previous test had unintended side-effects, since it
ran the --import command. new test merely lists keys and
validates output.

mark-in/securedrop-prov-upstream,mark-in/securedrop-prov-upstream,mark-in/securedrop-prov-upstream,mark-in/securedrop-prov-upstream