Add not_if to packages_repo.rb

Problem - try add apk-key on every run chef-client
And I got few errors. With timeout or network problems.
As example:
```---- Begin output of apt-key adv --keyserver keys.gnupg.net --recv 1C4CBDCDCD2EFD2A ----
STDOUT: Executing: gpg --ignore-time-conflict --no-options --no-default-keyring --secret-keyring /tmp/tmp.oiRYKunQxV --trustdb-name /etc/apt/trustdb.gpg --keyring /etc/apt/trusted.gpg --primary-keyring /etc/apt/trusted.gpg --keyserver keys.gnupg.net --recv 1C4CBDCDCD2EFD2A
gpgkeys: key 1C4CBDCDCD2EFD2A not found on keyserver
STDERR: gpg: requesting key CD2EFD2A from hkp server keys.gnupg.net
gpg: no valid OpenPGP data found.
gpg: Total number processed: 0
---- End output of apt-key adv --keyserver keys.gnupg.net --recv 1C4CBDCDCD2EFD2A ----```