fix multiple threads being started if sublimelint is reloaded
fix multiple threads being started if sublimelint is reloaded

SublimeLinter/SublimeLinter-for-ST2,benesch/sublime-linter,lunixbochs/sublimelint,jasonrhaas/SublimeLinter3,uschmidt83/SublimeLinter-for-ST2,ikappas/SublimeLinter3,simonzack/SublimeLinter3,SublimeLinter/SublimeLinter-for-ST2,tangledhelix/SublimeLinter-for-ST2,biodamasceno/SublimeLinter-for-ST2,zenlambda/SublimeLinter3,Raynos/SublimeLinter3-raynos,simonzack/SublimeLinter3,ikappas/SublimeLinter3,lunixbochs/sublimelint,smanolloff/SublimeLinter3,paulirish/SublimeLinter3,uschmidt83/SublimeLinter-for-ST2,paulirish/SublimeLinter3,tangledhelix/SublimeLinter-for-ST2,SublimeLinter/SublimeLinter3,zenlambda/SublimeLinter3,biodamasceno/SublimeLinter-for-ST2,SublimeLinter/SublimeLinter3,benesch/sublime-linter,smanolloff/SublimeLinter3,jasonrhaas/SublimeLinter3