install gnupg on download-wikimedia server

a download-wikimedia server (currently dataset2)
should have gnupg installed to check signatures of
files when adding them to download.wm.org

we do that,and it is currently installed on dataset2,
just puppetizing it

Change-Id: Ia09f8173cee49f4fdf6a1cbf28d8d1773683c240
Merge "install gnupg on download-wikimedia server" into production