fix: Close docker client when stopping the docker container

[rstcruzo]

Fixes the following warning

sys:1: ResourceWarning: unclosed <socket.socket fd=7, family=AddressFamily.AF_UNIX, type=SocketKind.SOCK_STREAM, proto=0, raddr=/Users/rodrigo/.docker/run/docker.sock>

Related to #379

[alexanderankin]

can you add a reproducer? i cannot replicate with:

PostgresContainer.py

from typing import Any

from sqlalchemy import create_engine, Engine, Connection, CursorResult, text
from testcontainers.postgres import PostgresContainer

p = PostgresContainer("postgres:14-alpine")


def main():
    p.start()
    engine: Engine = create_engine(p.get_connection_url())
    with engine.connect() as conn:
        conn: Connection = conn
        conn.execute(text("create table if not exists hero(name varchar(500) unique)"))
        conn.execute(text("insert into hero(name) values ('alice')"))
        conn.execute(text("insert into hero(name) values ('bob')"))
        with conn.execute(text('select * from hero')) as execute:
            execute: CursorResult[Any] = execute
            print(execute.fetchall())


if __name__ == '__main__':
    main()