Test increased connections

Author: alexeyr

.github/workflows/benchmark.yml

@@ -8,7 +8,7 @@ env:
   DEFAULT_RATE: &default_rate 'max'
   DEFAULT_DURATION_SEC: &default_duration_sec 30
   DEFAULT_REQUEST_TIMEOUT: &default_request_timeout '60s'
-  DEFAULT_CONNECTIONS: &default_connections 10
+  DEFAULT_CONNECTIONS: &default_connections 15
   DEFAULT_WEB_CONCURRENCY: &default_web_concurrency 4
   DEFAULT_RAILS_THREADS: &default_rails_threads 3
   DEFAULT_TOOLS: &default_tools 'fortio,vegeta,k6'