Signed URL does not respect host specified in StorageOptions

[frankyn]

When generating a signed URL the following code snippet doesn't respect the Host supplied by StorageOptions.

Storage storage = StorageOptions.getDefaultInstance().toBuilder().setHost("http://example.com/").build().getService();
URL signedUrl =  storage.signUrl(
                                          state.getBlobInfo(),
                                          1,
                                          TimeUnit.HOURS,
                                          SignUrlOption.httpMethod(HttpMethod.POST),
                                          SignUrlOption.withExtHeaders(
                                              ImmutableMap.of("x-goog-resumable", "start")),
                                          SignUrlOption.signWith(c.getServiceAccountSigner()),
                                          SignUrlOption.withV2Signature());

Edit to add:
When a custom endpoint is set on the client, Sign URLs and Post Policies should automatically use that domain.

Optional: allow users to set a custom hostname for Sign URL and Post policy methods

See: go/signurl-custom-endpoint-gcs