Regression from cd405cc9.
Parse_androidmanifests() can return 'Unknown' or 'Ignore' if it did not
find a version name. The check_tags() always returned the tag and
checkupdates_app() replaced the version by the tag in the 'Unknown'
case. Since cd405cc9 the tag is the hash and so the version would become
the hash as well. This patch moves the 'Unknown' check directly after
the Parse_androidmanifests().