Deletion of S3 objects fails for object paths starting with a slash

## Summary

When trying to delete all objects in an S3 bucket, the deletion fails for objects with a leading slash in their path.
The `delete_object` method returns `True` for these objects, even though they are not deleted.

## Detailed Information

To delete an S3 bucket we use `Container.list_objects()` and `delete_object` to first delete all objects in the bucket. This doesn't work for objects, where the object path starts with a slash. The `delete_object` function returns `True` for these objects even though they are not deleted because the DELETE request is sent to the wrong URL.
For example to delete the object `s3://container-name//path/to/object` the DELETE request is sent to
https://s3-eu-west-1.amazonaws.com/container-name/path/to/object
but it should be sent to this path instead:
https://s3-eu-west-1.amazonaws.com//container-name/path/to/object
The problem is that double slashes are replaced in the request URL in the method `Connection.morph_action_hook`. This is a similar issue to #1529.

To reproduce the issue, you can use the following code (replace credentials and bucket name):
```python
from libcloud.storage.types import Provider
from libcloud.storage.providers import get_driver

driver = get_driver(Provider.S3)
client = driver("key", "secret", region="eu-west-1")

container = client.get_container("container-name")
objects = container.list_objects()
for obj in objects:
client.delete_object(obj)
client.delete_container(container)
```
This will result in an `ContainerIsNotEmptyError` if the bucket "container-name" contains objects where the object path starts with a slash.

Libcloud version: 3.4.1
Python version: 3.7.12

Bắt đầu tại Connection.morph_action_hook và tái hiện vấn đề với ví dụ S3 bằng cách sử dụng một đường dẫn đối tượng bắt đầu bằng dấu gạch chéo. Theo dõi cách URL của yêu cầu DELETE được chuẩn hóa; hoàn tất khi dấu gạch chéo ở đầu được giữ nguyên, đối tượng thực sự bị xóa và bucket sau đó có thể được xóa.

Do mô hình lập chỉ mục viết ra từ nội dung của issue.