**Apache Airflow version**: 2.0.1

**Environment**:

- **Cloud provider or hardware configuration**: docker container
- **OS** (e.g. from /etc/os-release): `Debian GNU/Linux 10 (buster)`
- **Kernel** (e.g. `uname -a`): `Linux 69a18af222ff 3.10.0-1160.15.2.el7.x86_64 #1 SMP Thu Jan 21 16:15:07 EST 2021 x86_64 GNU/Linux`
- **Install tools**: `pip`
- **Others**: `azure` extras

**What happened**:

`airflow.providers.microsoft.azure.hooks.wasb.WasbHook.delete_file` unable to delete blobs if both conditions below are true:

* `is_prefix` argument set to `True`
* the target blobs contain at least one '/' character in their names


**What you expected to happen**:
All files starting with the specified prefix are removed.

The problem is caused by this line: https://github.com/apache/airflow/blob/73187871703bce22783a42db3d3cec9045ee1de2/airflow/providers/microsoft/azure/hooks/wasb.py#L410

By not specifying `delimiter = ''` the listed blobs won't be terminal blobs if the target blobs happen to contain the default delimiter (`/`) in their name

**How to reproduce it**:

For example, consider the following scenario. We have a blob container `cnt` with two files:
* `parent/file1`
* `parent/file2`

The following call should delete both files:
``` python
wasb_hook= WasbHook(...)
wasb_hook.delete_file(
    container_name='cnt',
    blob_name='parent',
    is_prefix=True,
)
```
But instead we get an error `Blob(s) not found: ('parent/',)`


tests/providers/microsoft/azure/hooks/test_wasb.py
hook = WasbHook(wasb_conn_id=self.shared_key_conn_id)
        hook.upload(
            container_name='mycontainer', blob_name='myblob', data=b'mydata', blob_type='BlockBlob', length=4
        )
        mock_cn_client = mock_service.return_value.get_container_client
        mock_cn_client.assert_called_once_with('mycontainer')
        mock_cn_client.return_value.get_blob_client.assert_called_once_with('myblob')
        mock_cn_client.return_value.get_blob_client.return_value.upload_blob.assert_called_once_with(
            b'mydata', 'BlockBlob', length=4
        )
    @mock.patch("airflow.providers.microsoft.azure.hooks.wasb.BlobServiceClient")
    def test_download(self, mock_service):
        container_client = mock_service.return_value.get_container_client
        blob_client = container_client.return_value.get_blob_client
        hook = WasbHook(wasb_conn_id=self.shared_key_conn_id)
        hook.download(container_name='mycontainer', blob_name='myblob', offset=2, length=4)
        container_client.assert_called_once_with('mycontainer')
        blob_client.assert_called_once_with('myblob')
        blob_client.return_value.download_blob.assert_called_once_with(offset=2, length=4)
    @mock.patch("airflow.providers.microsoft.azure.hooks.wasb.BlobServiceClient")
    def test_get_container_client(self, mock_service):
        hook = WasbHook(wasb_conn_id=self.shared_key_conn_id)
        hook._get_container_client('mycontainer')
        mock_service.return_value.get_container_client.assert_called_once_with('mycontainer')
    @mock.patch("airflow.providers.microsoft.azure.hooks.wasb.BlobServiceClient")
    def test_get_blob_client(self, mock_service):