Fix system_role title for role::jenkins::master::production

Gerrit change I90264df1c added a system_role resource for jenkins, but its
title is "role::zuul::production", which conflicts with line 41 of
manifests/role/zuul.pp@7c3e1e89. I presume Antoine was simply using his early
work as a reference and did a s/zuul/jenkins in one place (the description) but
not the other.

Change-Id: I4696578a7e8521ec6cf08fd21ae5ea3a2e5e3595