Controller Projects::IssuesController#create executes more than 100 SQL queries (7 day: 130k hits, average 87 queries)

This controller executes more than 100 SQL queries, the maximum number of queries allowed as per MR https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/16466. The number of queries should be reduced to less than 100 and the corresponding whitelisted sections of code (Gitlab::QueryLimiting.whitelist('...')) should be removed.