Do not populate resource cache when resource_matching is disabled

Previously the `resource_matching` feature flag would only guard against
returning resource matches to users who queried the
`/v3/resource_matches` endpoint. However, it would not prevent packages
from being uploaded to the resource cache, causing blobstores to bloat
unnecessarily. This commit updates the behavior and only uploads package
bits to the resource cache blobstore when the feature flag is enabled.

[#172640608](https://www.pivotaltracker.com/story/show/172640608)

Author: MerricdeLauney

lib/cloud_controller/packager/shared_bits_packer.rb

@@ -55,7 +55,7 @@ def match_resources_and_validate_package(root_path, uploaded_package_zip, cached
         if package_zip_exists?(uploaded_package_zip)
           copy_uploaded_package(uploaded_package_zip, app_packager)
           validate_size!(app_packager)
-          populate_resource_cache(app_packager, app_contents_path)
+          populate_resource_cache(app_packager, app_contents_path) unless VCAP::CloudController::FeatureFlag.disabled?(:resource_matching)
         end
 
         append_matched_resources(app_packager, cached_files_fingerprints, root_path)

spec/unit/lib/cloud_controller/packager/local_bits_packer_spec.rb

@@ -176,6 +176,18 @@ module CloudController::Packager
           packer.send_package_to_blobstore(blobstore_key, uploaded_files_path, cached_files_fingerprints)
         end
 
+        context 'when the resource_matching feature flag is disabled' do
+          before do
+            VCAP::CloudController::FeatureFlag.make(name: 'resource_matching', enabled: false)
+          end
+
+          it 'does not upload any app bits to the app bit cache' do
+            packer.send_package_to_blobstore(blobstore_key, uploaded_files_path, cached_files_fingerprints)
+            sha_of_bye_file_in_good_zip = 'ee9e51458f4642f48efe956962058245ee7127b1'
+            expect(global_app_bits_cache.exists?(sha_of_bye_file_in_good_zip)).to be false
+          end
+        end
+
         context 'when there is an unreadable directory in the zip' do
           let(:input_zip) { File.join(Paths::FIXTURES, 'app_packager_zips', 'unreadable_dir.zip') }
           let(:input_zip_file_path) { File.join(local_tmp_dir, 'unreadable_dir.zip') }