perf tests: fix arg passing

- now that we wrap the perf tests in a Rails wrapper, the outer `ARGV`
  needs to be passed to the inner one
- fix straggler that wasn't previously converted to use an iteration
  count

test/performance/script/runner

@@ -9,4 +9,4 @@ require_relative '../rails_app/config/boot'
 require 'rails/command'
 require_relative '../lib/performance'
 
-Rails::Command.invoke(:runner, %w[Performance::Runner.new.run_and_report])
+Rails::Command.invoke(:runner, %w[Performance::Runner.new.run_and_report] + ARGV)

test/performance/suites/agent_module.rb

@@ -9,7 +9,7 @@ class AgentModuleTest < Performance::TestCase
   ITERATIONS = 50_000
 
   def test_increment_metric_by_1
-    measure do
+    measure(ITERATIONS) do
       NewRelic::Agent.increment_metric(METRIC)
     end
   end