Commit email and LDAP email don't match with hooks

Merged username-removed-192314 requested to merge kalibyrn/gitlab-ee:downcase-emails-for-hook into master

When using LDAP groups, emails are downcased. The commit email also needs to be downcased during comparisons, otherwise the pre-receive hook will cause a failure if the user hasn't chosen to downcase his own Git entry.

Refer to