An automated WordPress update from 4.0.1 to 4.2.2 has failed to complete

I am running a multisite setup op wordpress 4.0.1 and want to update it to 4.2.2. When i try to make a automated udpate i get error saying “An Automated WordPress update has failed to complete”. More info on it shows that

Unpacking the update…

Could not create directory.

Installation Failed

I search through forums and found some posts saying to remove upgrade dir under ./wp-content/ and also .maintenance file in web root of wordpress. Now i removed upgrade dir but i could find .maintenance file.

I am running having nginx as my web-server and my wordpress directory is having nginx as owner and permissions are 775. How shall i resolve this?