Don't reinit displaced when it's not needed
Don't reinit displaced when it's not needed

In idaholab/falcon#106 there is a displaced problem and mesh but
no objects are actually using it. We guard other functions like
`setCurrentSubdomainID` so we also must guard other "downstream"
functions that might use that subdomain ID like the one now guarded
in this PR

idaholab/moose,idaholab/moose,idaholab/moose,idaholab/moose,idaholab/moose