Perf: task helper perf improvements for catch and finally.  Task creation is still ridiculously expensive, so reuse the completed task in the mainline case for catch and finally.
Perf: task helper perf improvements for catch and finally.  Task creation is still ridiculously expensive, so reuse the completed task in the mainline case for catch and finally.

abkmr/WebApi,congysu/WebApi,yonglehou/WebApi,scz2011/WebApi,yonglehou/WebApi,congysu/WebApi,chimpinano/WebApi,lungisam/WebApi,LianwMS/WebApi,lungisam/WebApi,chimpinano/WebApi,abkmr/WebApi,lewischeng-ms/WebApi,lewischeng-ms/WebApi,LianwMS/WebApi,scz2011/WebApi