key id's longer than 8 characters are always downloaded/retreived from key servers/sources

some repos (like percona apt repo) have key id's longer than 8 characters and if given key id is longer than 8 characters, it won't be matched on "apt-key list | grep KEY" and marked unlisted which will force puppet to download/retreive it on each run.

```ruby
  apt::source {
    "percona":
      location          => "http://repo.percona.com/apt",
      release           => $::lsbdistcodename,
      repos             => "main",
      include_src       => false,
      key               => "1C4CBDCDCD2EFD2A",
      key_server        => "keys.gnupg.net",
  }
```