Merge branch 'use-remote-ip-for-akismet' into 'master'

Use ActionDispatch Remote IP for Akismet checking

Previously all remote IPs appeared at 127.0.0.1, which made Akismet
not very useful. Using the ActionDispatch Remote IP (http://api.rubyonrails.org/classes/ActionDispatch/RemoteIp.html)
should provide more reliable results.

Closes #16629

See merge request !3961