sync/atomic: do not run TestStoreLoadSeq for too long (fix windows builder)
sync/atomic: do not run TestStoreLoadSeq for too long (fix windows builder)

R=golang-dev, adg
CC=golang-dev
http://codereview.appspot.com/4962057

npe9/noahevans-go9,rflanagan/reginaldflanagan-project1,rflanagan/reginaldflanagan-project1,Triskite/willstone-goclone,bryanxu/go-zh,Triskite/willstone-goclone,bryanxu/go-zh,npe9/noahevans-go9,webfd/go-zh,mhennings/marcohennings-go,d0f/go-zh,mhennings/marcohennings-go,npe9/noahevans-go9,bryanxu/go-zh,d0f/go-zh,scirelli/scirelli-go,scirelli/scirelli-go,mhennings/marcohennings-go,sanjosh/sanjos100-tipc,Triskite/willstone-goclone,rdp/rogerpack2005-golang,glycerine/jeaten-go-arrayof-structof,Triskite/willstone-goclone,bryanxu/go-zh,rflanagan/reginaldflanagan-project1,bryanxu/go-zh,rflanagan/reginaldflanagan-project1,d0f/go-zh,rdp/rogerpack2005-golang,scirelli/scirelli-go,d0f/go-zh,d0f/go-zh,npe9/noahevans-go9,mhennings/marcohennings-go,rdp/rogerpack2005-golang,rdp/rogerpack2005-golang,sanjosh/sanjos100-tipc,rdp/rogerpack2005-golang,webfd/go-zh,Triskite/willstone-goclone,bryanxu/go-zh,d0f/go-zh,mhennings/marcohennings-go,rdp/rogerpack2005-golang,sanjosh/sanjos100-tipc,sanjosh/sanjos100-tipc,glycerine/jeaten-go-arrayof-structof,d0f/go-zh,scirelli/scirelli-go,Triskite/willstone-goclone,scirelli/scirelli-go,sanjosh/sanjos100-tipc,rdp/rogerpack2005-golang,sanjosh/sanjos100-tipc,d0f/go-zh,webfd/go-zh,npe9/noahevans-go9,sanjosh/sanjos100-tipc,sanjosh/sanjos100-tipc,rflanagan/reginaldflanagan-project1,bryanxu/go-zh,mhennings/marcohennings-go,scirelli/scirelli-go,webfd/go-zh,glycerine/jeaten-go-arrayof-structof,glycerine/jeaten-go-arrayof-structof,rflanagan/reginaldflanagan-project1,glycerine/jeaten-go-arrayof-structof,webfd/go-zh,Triskite/willstone-goclone,webfd/go-zh,npe9/noahevans-go9,rdp/rogerpack2005-golang,glycerine/jeaten-go-arrayof-structof,scirelli/scirelli-go,rflanagan/reginaldflanagan-project1,npe9/noahevans-go9,scirelli/scirelli-go,bryanxu/go-zh,glycerine/jeaten-go-arrayof-structof,glycerine/jeaten-go-arrayof-structof,Triskite/willstone-goclone,webfd/go-zh,mhennings/marcohennings-go,npe9/noahevans-go9,mhennings/marcohennings-go,webfd/go-zh,rflanagan/reginaldflanagan-project1