Remove "threadpool_size" config parameter

* was only used for Thin/EventMachine

Author: jochenehret

config/bosh-lite.yml

@@ -268,5 +268,3 @@ diego:
   pid_limit: 1024
 
 shared_isolation_segment_name: shared
-
-threadpool_size: 20

config/cloud_controller.yml

@@ -394,7 +394,6 @@ locket:
   cert_file: 'spec/fixtures/certs/bbs_client.crt'
   key_file: 'spec/fixtures/certs/bbs_client.key'
 
-threadpool_size: 20
 webserver: puma
 default_app_lifecycle: buildpack
 custom_metric_tag_prefix_list: ["metric.tag.cloudfoundry.org"]

lib/cloud_controller/config_schemas/api_schema.rb

@@ -315,7 +315,6 @@ class ApiSchema < VCAP::Config
           },
 
           request_timeout_in_seconds: Integer,
-          threadpool_size: Integer,
           skip_cert_verify: bool,
 
           webserver: String, # currently only puma

spec/fixtures/config/port_8181_config.yml

@@ -229,5 +229,3 @@ credhub_api:
 
 credential_references:
   interpolate_service_bindings: true
-
-threadpool_size: 20

spec/unit/lib/cloud_controller/config_spec.rb

@@ -209,10 +209,6 @@ module VCAP::CloudController
               expect(config[:request_timeout_in_seconds]).to eq(600)
             end
 
-            it 'preserves the threadpool_size value from the file' do
-              expect(config[:threadpool_size]).to eq(20)
-            end
-
             it 'preserves the value of the staging auth user/password' do
               expect(config[:staging][:auth][:user]).to eq('bob')
               expect(config[:staging][:auth][:password]).to eq('laura')