PacketFactory.h: Fix two-stage lookup issue.
PacketFactory.h: Fix two-stage lookup issue.

Found by Clang.

MichaelMcDonnell/vrjuggler,LiuKeHua/vrjuggler,godbyk/vrjuggler-upstream-old,vrjuggler/vrjuggler,godbyk/vrjuggler-upstream-old,MichaelMcDonnell/vrjuggler,vrjuggler/vrjuggler,godbyk/vrjuggler-upstream-old,vrjuggler/vrjuggler,vrjuggler/vrjuggler,vrjuggler/vrjuggler,vancegroup-mirrors/vrjuggler,LiuKeHua/vrjuggler,godbyk/vrjuggler-upstream-old,LiuKeHua/vrjuggler,vrjuggler/vrjuggler,vrjuggler/vrjuggler,godbyk/vrjuggler-upstream-old,LiuKeHua/vrjuggler,vrjuggler/vrjuggler,godbyk/vrjuggler-upstream-old,MichaelMcDonnell/vrjuggler,MichaelMcDonnell/vrjuggler,LiuKeHua/vrjuggler,LiuKeHua/vrjuggler,vancegroup-mirrors/vrjuggler,MichaelMcDonnell/vrjuggler,MichaelMcDonnell/vrjuggler,vancegroup-mirrors/vrjuggler,LiuKeHua/vrjuggler,vancegroup-mirrors/vrjuggler,vancegroup-mirrors/vrjuggler,vancegroup-mirrors/vrjuggler,MichaelMcDonnell/vrjuggler,LiuKeHua/vrjuggler,MichaelMcDonnell/vrjuggler