fix overlap poll request return too fast problem. this situation
happened when page refresh .in commit bd4832 ,we reserved previous
suspended long poll when overlap poll request arrived. and return
immediately .but if user refresh whole page,new poll request will always
return immediately until previous poll request returned, this leads too
many request/response. with this commit, previous poll is flushed
instead of reserved. client side should avoid two simultaneously poll
refactor http access code
refactor most http test
add poll overlap test
some page reload message load fix