Add the ability to turn off image pulling.

Wait... aren't all of our other policies and such camelCase?

----- Original Message -----
> > @@ -173,6 +173,16 @@ type LivenessProbe struct {
> >  	InitialDelaySeconds int64 `yaml:"initialDelaySeconds,omitempty"
> >  	json:"initialDelaySeconds,omitempty"`
> >  }
> >  
> > +// PullPolicy describes a policy for if/when to pull a container image
> > +type PullPolicy string
> > +
> > +const (
> > +	// Always attempt to pull the latest image
> > +	PullNewest PullPolicy = "PULL_NEWEST"
> 
> As precedent we define protocol as TCP and UDP, further supporting ALL_CAPS
> mode.  If I get to be decider I decide ALL_CAPS.
> 
> ---
> Reply to this email directly or view it on GitHub:
> https://github.com/GoogleCloudPlatform/kubernetes/pull/1458/files#r18102177