Parent Selection -- Host Marking -- Handle pRec == nullptr and wrap-around cases.
Parent Selection -- Host Marking -- Handle pRec == nullptr and wrap-around cases.

* Do not call pStatus.getHostStatus() is pRec == nullptr just set to HOST_STATUS_INIT.

* Add !pRec as valid condition for further searching of parents.

* Changed !prtmp to !pRec to enhance clarity.

* Added requirement that selected parent must be UP prior to populating the
  result structure otherwise an invalid choice may be returned in the case
  of all rings wrapped with no valid results.

duke8253/trafficserver,dyrock/trafficserver,dyrock/trafficserver,persiaAziz/trafficserver,persiaAziz/trafficserver,SolidWallOfCode/trafficserver,dyrock/trafficserver,bryancall/trafficserver,chitianhao/trafficserver,chitianhao/trafficserver,vmamidi/trafficserver,chitianhao/trafficserver,duke8253/trafficserver,chitianhao/trafficserver,davidbz/trafficserver,vmamidi/trafficserver,bryancall/trafficserver,SolidWallOfCode/trafficserver,davidbz/trafficserver,dyrock/trafficserver,persiaAziz/trafficserver,dyrock/trafficserver,persiaAziz/trafficserver,davidbz/trafficserver,SolidWallOfCode/trafficserver,pbchou/trafficserver,bryancall/trafficserver,davidbz/trafficserver,chitianhao/trafficserver,duke8253/trafficserver,dyrock/trafficserver,dyrock/trafficserver,pbchou/trafficserver,SolidWallOfCode/trafficserver,duke8253/trafficserver,persiaAziz/trafficserver,bryancall/trafficserver,bryancall/trafficserver,davidbz/trafficserver,SolidWallOfCode/trafficserver,duke8253/trafficserver,duke8253/trafficserver,duke8253/trafficserver,SolidWallOfCode/trafficserver,persiaAziz/trafficserver,pbchou/trafficserver,persiaAziz/trafficserver,bryancall/trafficserver,pbchou/trafficserver,vmamidi/trafficserver,pbchou/trafficserver,vmamidi/trafficserver,davidbz/trafficserver,vmamidi/trafficserver,persiaAziz/trafficserver,vmamidi/trafficserver,chitianhao/trafficserver,pbchou/trafficserver,chitianhao/trafficserver,SolidWallOfCode/trafficserver