Allow overriding storage bucket in acceptance tests (#2531)

Author: dazuma

google-cloud-storage/acceptance/storage/file_test.rb

@@ -29,7 +29,9 @@
       big:  { path: "acceptance/data/three-mb-file.tif" } }
   end
 
-  let(:bucket_public_test_name) { "storage-library-test-bucket" }
+  let(:bucket_public_test_name) {
+    ENV["GCLOUD_TEST_STORAGE_BUCKET"] || "storage-library-test-bucket"
+  }
   let(:file_public_test_gzip_name) { "gzipped-text.txt" }  # content is "hello world"
 
   before do

google-cloud-storage/acceptance/storage/filename_test.rb

@@ -15,7 +15,9 @@
 require "storage_helper"
 
 describe Google::Cloud::Storage::File, :storage do
-  let(:bucket_name) { "storage-library-test-bucket" }
+  let(:bucket_name) {
+    ENV["GCLOUD_TEST_STORAGE_BUCKET"] || "storage-library-test-bucket"
+  }
   let :bucket do
     storage.bucket(bucket_name)
   end