Fix a deadlock during BGC thread creation
Fix a deadlock during BGC thread creation

[tfs-changeset: 1616430]

sandreenko/corert,tijoytom/corert,gregkalapos/corert,gregkalapos/corert,kyulee1/corert,shrah/corert,krytarowski/corert,tijoytom/corert,botaberg/corert,kyulee1/corert,botaberg/corert,krytarowski/corert,sandreenko/corert,sandreenko/corert,botaberg/corert,shrah/corert,shrah/corert,yizhang82/corert,tijoytom/corert,botaberg/corert,yizhang82/corert,sandreenko/corert,tijoytom/corert,yizhang82/corert,krytarowski/corert,gregkalapos/corert,krytarowski/corert,gregkalapos/corert,yizhang82/corert,kyulee1/corert,kyulee1/corert,shrah/corert