fix gpg key retrieval

getting gpg keys from key-servers is still broken in the latest release (see Bug #11380).

the problem is, that email addresses are not correctly extracted from the received keys list, thus all keys are rejected.

commit 425bcf0cf8e5686fe273ff9345be1e06bf5a487b incorectly copy/pasted the solution from my original pull request. this commit fixes the copy/paste error.

just a comment: how would i add tests for this part of the code