Install puppetlast cronjob under a usable name.

That is, install it as /etc/cron.d/puppetlast,
and cleanup the old buggy /etc/cron.d/puppetlast.cron.

As cron(8) says about /etc/cron.d/: "For example, any file containing dots will
be ignored."
checklastrun cronjob: only pass output through in imperfect situations.

That is, silence it (and avoid nagging the administrators with email)
when all hosts are OK, and puppetlast exits with return code 0.
Merge remote-tracking branch 'intrigeri/bugfix/have_puppetlast_cronjob_run'