fix ui jumping flaw  when it comes back to refreshing state.
fix ui jumping flaw  when it comes back to refreshing state.

CoderMJLee/MJRefresh,yaohua1179/MJRefresh,woodpower/MJRefresh,petyou/MJRefresh,jingchunYuan/MJRefresh,ShannonChenCHN/MJRefresh,CoderMJLee/MJRefresh,xiaozi4624/MJRefresh,russellyi/MJRefresh