refactor: Removed extra code from DeletePost handler
refactor: Removed extra code from DeletePost handler

Removed user = self.user from DeletePost handler
and replaces all occurrences of 'user' with
'self.user'.

tstillwell2k17/GAE-BLOGAPP-MULTI_USER-DEMO,tstillwell2k17/GAE-BLOGAPP-MULTI_USER-DEMO,tstillwell2k17/GAE-BLOGAPP-MULTI_USER-DEMO