Unable to install plugins if user jenkins has a duplicate UID

I need to have jenkins sharing UID with www-data and I had problems when trying to install modules

I found out that puppet doesnt like much trying to run commands as user 'jenkins' when he has UID 33 and other user also has UID 33

To workaround it, I do the exec to download the plugin as root, and then use a file resource to correct file ownership
That seems to work fine :)

I did a previous pull request, but cancelled it because of its dirtyness. Sorry