Handle leading slash in samba path

[fredthomsen]

Fix issue that occurs when the path to a file on a samba share has a
slash prepended to it, then the SambaHook will treat the path as the
host instead likely resulting trying to connect to the wrong samba host.

For example, this code:

hook = SambaHook('samba_test')
hook.push_from_local(
    "/Sales/TestData/sometestfile.txt",
    "/tmp/somefile",
)

resulted in:

airflow/providers/samba/hooks/samba.py:246: in push_from_local
    with open(local_filepath, "rb") as f, self.open_file(destination_filepath, mode="wb") as g:
airflow/providers/samba/hooks/samba.py:135: in open_file
    **self._conn_kwargs,
/usr/local/lib/python3.6/site-packages/smbclient/_os.py:370: in open_file
    file_attributes=file_attributes, **kwargs)
/usr/local/lib/python3.6/site-packages/smbclient/_io.py:374: in __init__
    tree, fd_path = get_smb_tree(path, **kwargs)
/usr/local/lib/python3.6/site-packages/smbclient/_pool.py:301: in get_smb_tree
    auth_protocol=auth_protocol)
/usr/local/lib/python3.6/site-packages/smbclient/_pool.py:358: in register_session
    connection.connect(timeout=connection_timeout)
/usr/local/lib/python3.6/site-packages/smbprotocol/connection.py:719: in connect
    self.transport.connect()
/usr/local/lib/python3.6/site-packages/smbprotocol/transport.py:74: ValueError

ValueError: Failed to connect to 'Sales:445': [Errno -2] Name or service not known

---

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[github-actions]

The PR is likely OK to be merged with just subset of tests for default Python and Database versions without running the full matrix of tests, because it does not modify the core of Airflow. If the committers decide that the full tests matrix is needed, they will add the label 'full tests needed'. Then you should rebase to the latest main or amend the last commit of the PR, and push it with --force-with-lease.