Run most non-sensitive jobs on single-use workers

* doc/source/jjb.rst
* doc/source/stackforge.rst: Update examples to recommend
bare-precise nodes in new job configuration.

* modules/openstack_project/files/jenkins_job_builder/config/*.yaml:
Change the node label for all jobs opreviously using precise to use
bare-precise instead.

* modules/openstack_project/files/zuul/layout.yaml: Get rid of the
transitional matches for setting the single use parameter function
on specific job names and just set it on everything as a default.
Add patterns for jobs which need long-running slaves to apply a
reusable node parameter function instead.

* modules/openstack_project/files/zuul/openstack_functions.py: Add a
parameter function for reusable nodes which refrains from enabling
auto-offline behavior.

* modules/openstack_project/templates/nodepool/nodepool.yaml.erb:
Double the minimum ready bare-precise nodes to accommodate
additional load.

Change-Id: I2a90c5b120a50bb8033c891702185f054ee84d35
Merge "Run most non-sensitive jobs on single-use workers"