Fix recalculating UTC task times in task monitor
Fix recalculating UTC task times in task monitor

Fixes #257

I believe that task.timestamp should not be touched, as everything is in UTC now.

Need someone who knows the project better, to verify if my assumptions are correct.

See https://github.com/mher/flower/issues/257#issuecomment-52766817 for details
asmodehn/flower,allengaller/flower,pygeek/flower,marrybird/flower,asmodehn/flower,allengaller/flower,asmodehn/flower,Lingling7/flower,pygeek/flower,raphaelmerx/flower,ucb-bar/bar-crawl-web,lucius-feng/flower,raphaelmerx/flower,tellapart/flower,Lingling7/flower,getupcloud/flower,alexmojaki/flower,ChinaQuants/flower,barseghyanartur/flower,allengaller/flower,tellapart/flower,jzhou77/flower,getupcloud/flower,barseghyanartur/flower,ucb-bar/bar-crawl-web,lucius-feng/flower,ucb-bar/bar-crawl-web,barseghyanartur/flower,marrybird/flower,pj/flower,alexmojaki/flower,pj/flower,getupcloud/flower,marrybird/flower,tellapart/flower,jzhou77/flower,ChinaQuants/flower,lucius-feng/flower,ChinaQuants/flower,raphaelmerx/flower,alexmojaki/flower,pj/flower,Lingling7/flower,pygeek/flower,jzhou77/flower