fix(api): do not run API multi-threaded

It's multi-processing, that will be enough paralellism.
The way the PDNS change tracker uses Django signals is not multi-
threading-safe.

Do not re-enable multi-threading unless the change tracker can
handle it!

api/uwsgi.ini

@@ -3,7 +3,7 @@ socket = [::]:3031
 chdir = /usr/src/app/
 wsgi-file = api/wsgi.py
 processes = 64
-threads = 4
+threads = 1
 #stats = 127.0.0.1:9191
 
 #master = true