Raise DockerException for invalid ports in parse_host()

[semx]

Problem

parse_host() mishandles invalid ports in the tcp/ssh branch.

1. A raw ValueError escapes instead of DockerException.
The port is read via parsed_url.port, and urllib's .port property raises ValueError for an out-of-range or non-numeric port. That error propagates unwrapped, even though the rest of parse_host() — and the invalid_hosts test contract in tests/unit/utils_test.py — guarantees invalid input raises DockerException. A user with a malformed DOCKER_HOST gets an opaque ValueError that except DockerException won't catch.

>>> from docker.utils import parse_host
>>> parse_host('tcp://host:99999')
ValueError: Port out of range 0-65535
>>> parse_host('tcp://host:notaport')
ValueError: Port could not be cast to integer value as 'notaport'

2. ssh://host:0 silently produces a malformed result.
parsed_url.port or 0 collapses an explicit :0 into the "no port given" case. For ssh the code then rebuilds netloc = f'{parsed_url.netloc}:{port}', but parsed_url.netloc still ends in :0, so :22 is appended to it:

>>> parse_host('ssh://host:0')
'ssh://host:0:22'

tcp://host:0 is already rejected with DockerException, so the two protocols were inconsistent.

Fix

Wrap the parsed_url.port access, distinguish a missing port (None) from an explicitly invalid one, and reject port 0 for both protocols:

try:
    port = parsed_url.port
except ValueError as e:
    raise errors.DockerException(f'Invalid bind address format: {addr}') from e
if port is None:
    if proto != 'ssh':
        raise errors.DockerException(f'Invalid bind address format: port is required: {addr}')
    port = 22
    netloc = f'{parsed_url.netloc}:{port}'
elif port <= 0:
    raise errors.DockerException(f'Invalid bind address format: port is required: {addr}')

After the change:

tcp://host:99999     -> DockerException: Invalid bind address format
tcp://host:notaport  -> DockerException: Invalid bind address format
ssh://host:0         -> DockerException: Invalid bind address format: port is required

Valid hosts are unaffected (ssh://host → ssh://host:22, tcp://host:2375 → http://host:2375, empty host → 127.0.0.1, IPv6, etc.).

Tests

Added tcp://host:0, ssh://host:0, tcp://host:99999 and tcp://host:notaport to the invalid_hosts list in tests/unit/utils_test.py. The full utils_test.py suite (73 tests) passes.