caff: do not stop after importing all keys from the user's gpg dir

Even if all keys to sign were found in the user's normal gpg keyrings we still
need to import them (again) from any keyrings passed with --key-files - the
keys there might be newer, containing new subkeys (for encryption), uids (for
signing) or revocations.

git-svn-id: svn://svn.debian.org/pgp-tools/trunk@474 b513b33f-fedd-0310-b452-c3deb5f4c849