OpenVR 1.5.17 was released, so adding support for that.
#rb sdkupgrade
#ROBOMERGE-OWNER: ben.marsh
#ROBOMERGE-AUTHOR: joe.conley
#ROBOMERGE-SOURCE: CL 7478901 in //UE4/Release-4.23/... via CL 7478906
#ROBOMERGE-BOT: BUILD (Main -> Dev-Build) (v372-7473910)
[CL 7587662 by joe conley in Dev-Build branch]