If Workspace.open finds existing item, yield event loop
If Workspace.open finds existing item, yield event loop

This ensures that the function always behaves asynchronously regardless
of the state of the workspace.

/cc @maxbrunsfeld

Signed-off-by: Antonio Scandurra <0e17b4d558b07b12cd221e35c438be378ba118cf@github.com>

andrewleverette/atom,stinsonga/atom,AlexxNica/atom,decaffeinate-examples/atom,decaffeinate-examples/atom,FIT-CSE2410-A-Bombs/atom,liuderchi/atom,liuderchi/atom,ardeshirj/atom,stinsonga/atom,decaffeinate-examples/atom,sotayamashita/atom,kevinrenaers/atom,Mokolea/atom,stinsonga/atom,CraZySacX/atom,kevinrenaers/atom,Mokolea/atom,ardeshirj/atom,brettle/atom,Arcanemagus/atom,xream/atom,Mokolea/atom,brettle/atom,atom/atom,liuderchi/atom,brettle/atom,PKRoma/atom,atom/atom,Arcanemagus/atom,ardeshirj/atom,decaffeinate-examples/atom,kevinrenaers/atom,andrewleverette/atom,andrewleverette/atom,Arcanemagus/atom,xream/atom,AlexxNica/atom,AlexxNica/atom,xream/atom,CraZySacX/atom,sotayamashita/atom,PKRoma/atom,t9md/atom,stinsonga/atom,FIT-CSE2410-A-Bombs/atom,atom/atom,PKRoma/atom,FIT-CSE2410-A-Bombs/atom,t9md/atom,liuderchi/atom,t9md/atom,CraZySacX/atom,sotayamashita/atom