feat: allow Sentry uWSGI-plugin to be optional

Use ENABLE_SENTRY_UWSGI_PLUGIN-flag to control
Sentry uWSGI-plugin usage. Disable it by default.

Refs: NS-180

Author: mhieta

.prod/uwsgi.ini

@@ -42,7 +42,7 @@ ignore-sigpipe = true
 ignore-write-errors = true
 disable-write-exception = true
 
-if-env = SENTRY_DSN
+if-env = ENABLE_SENTRY_UWSGI_PLUGIN
 print = Enabled sentry logging for uWSGI
 plugin-dir = /usr/local/lib/uwsgi/plugins
 plugin = sentry