RequirementMachine: Don't change concrete type to ErrorType in case of a conflict
RequirementMachine: Don't change concrete type to ErrorType in case of a conflict

This more closely matches the existing behavior of the GSB, where
conflicts are diagnosed but we don't drop all concrete type
requirements on that type parameter altogether.

hooman/swift,parkera/swift,JGiola/swift,rudkx/swift,parkera/swift,hooman/swift,apple/swift,glessard/swift,benlangmuir/swift,glessard/swift,parkera/swift,xwu/swift,rudkx/swift,tkremenek/swift,apple/swift,glessard/swift,roambotics/swift,parkera/swift,xwu/swift,apple/swift,benlangmuir/swift,hooman/swift,tkremenek/swift,JGiola/swift,JGiola/swift,parkera/swift,rudkx/swift,apple/swift,ahoppen/swift,parkera/swift,roambotics/swift,ahoppen/swift,apple/swift,tkremenek/swift,xwu/swift,gregomni/swift,parkera/swift,tkremenek/swift,roambotics/swift,hooman/swift,apple/swift,rudkx/swift,atrick/swift,ahoppen/swift,glessard/swift,glessard/swift,atrick/swift,benlangmuir/swift,benlangmuir/swift,gregomni/swift,xwu/swift,glessard/swift,ahoppen/swift,roambotics/swift,xwu/swift,gregomni/swift,rudkx/swift,JGiola/swift,parkera/swift,tkremenek/swift,tkremenek/swift,JGiola/swift,JGiola/swift,gregomni/swift,atrick/swift,hooman/swift,ahoppen/swift,atrick/swift,hooman/swift,gregomni/swift,roambotics/swift,rudkx/swift,roambotics/swift,tkremenek/swift,ahoppen/swift,xwu/swift,hooman/swift,atrick/swift,atrick/swift,gregomni/swift,benlangmuir/swift,xwu/swift,benlangmuir/swift