create_sibling_ria does not release IO handler resources properly

[mih]

Here is the word-diff of what needs to change (i.e., wrapping the io object into a closing context manager).

Without this change, a remote shell (with SSHRemoteIO) is not properly closed until process/command exit.

diff --git a/datalad/distributed/create_sibling_ria.py b/datalad/distributed/create_sibling_ria.py
index 15ccd2df6..b43de0712 100644
--- a/datalad/distributed/create_sibling_ria.py
+++ b/datalad/distributed/create_sibling_ria.py
@@ -403,29 +403,29 @@ class CreateSiblingRia(Interface):
        #         command abstractions
        #       - more generally consider store creation a dedicated command or
        #         option
        [-io = SSHRemoteIO(ssh_host)-]{+from contextlib import closing+}
{+        with closing(SSHRemoteIO(ssh_host)+} if ssh_host else [-LocalIO()-]{+LocalIO()) as io:+}
            try:
                # determine the existence of a store by trying to read its layout.
                # Because this raises a FileNotFound error if non-existent, we need
                # to catch it
                io.read_file(local_base_path / 'ria-layout-version')
            except (FileNotFoundError, RIARemoteError, RemoteCommandFailedError) as e:
                if not new_store_ok:
                    # we're instructed to only act in case of an existing RIA store
                    res = get_status_dict(
                        status='error',
                        message="No store found at '{}'. Forgot "
                                "--new-store-ok ?".format(local_base_path),
                        **res_kwargs)
                    yield res
                    return

            log_progress(
                lgr.info, 'create-sibling-ria',
                'Creating a new RIA store at %s', local_base_path,
            )
            create_store(io, local_base_path, '1')

        yield from _create_sibling_ria(
            ds,