Fix: add 3sec delay in instance coco cmd to ensure VM is starting

[philogicae]

Bug

• When using aleph instance confidential, the cmd fails at confidential_start() (after confidential_init_session()) returning "bad request"

Self proofreading checklist

• The new code clear, easy to read and well commented.
• New code does not duplicate the functions of builtin or popular libraries.
• An LLM was used to review the new code and look for simplifications.
• New classes and functions contain docstrings explaining what they provide.
• All new code is covered by relevant tests.

Changes

• Add 3sec delay before confidential_start() in aleph instance confidential cmd to ensure VM is starting.

[github-actions]

Failed to retrieve llama text: POST 500: Traceback (most recent call last):
File "/usr/local/lib/python3.9/dist-packages/aiohttp/connector.py", line 980, in _wrap_create_connection
return await self._loop.create_connection(*args, **kwargs) # type: ignore[return-value] # noqa
File "/usr/lib/python3.9/asyncio/base_events.py", line 1056, in create_connection
raise exceptions[0]
File "/usr/lib/python3.9/asyncio/base_events.py", line 1041, in create_connection
sock = await self._connect_sock(
File "/usr/lib/python3.9/asyncio/base_events.py", line 955, in _connect_sock
await self.sock_connect(sock, address)
File "/usr/lib/python3.9/asyncio/selector_events.py", line 502, in sock_connect
return await fut
File "/usr/lib/python3.9/asyncio/selector_events.py", line 537, in _sock_connect_cb
raise OSError(err, f'Connect call failed {address}')
ConnectionRefusedError: [Errno 111] Connect call failed ('::1', 8080, 0, 0)

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
File "/root/init1.py", line 406, in process_instruction
headers, body, output, output_data = await run_executable_http(
File "/root/init1.py", line 342, in run_executable_http
headers, body = await make_request(session, scope)
File "/root/init1.py", line 311, in make_request
async with session.request(
File "/usr/local/lib/python3.9/dist-packages/aiohttp/client.py", line 1141, in aenter
self._resp = await self._coro
File "/usr/local/lib/python3.9/dist-packages/aiohttp/client.py", line 536, in _request
conn = await self._connector.connect(
File "/usr/local/lib/python3.9/dist-packages/aiohttp/connector.py", line 540, in connect
proto = await self._create_connection(req, traces, timeout)
File "/usr/local/lib/python3.9/dist-packages/aiohttp/connector.py", line 901, in _create_connection
_, proto = await self._create_direct_connection(req, traces, timeout)
File "/usr/local/lib/python3.9/dist-packages/aiohttp/connector.py", line 1206, in _create_direct_connection
raise last_exc
File "/usr/local/lib/python3.9/dist-packages/aiohttp/connector.py", line 1175, in _create_direct_connection
transp, proto = await self._wrap_create_connection(
File "/usr/local/lib/python3.9/dist-packages/aiohttp/connector.py", line 988, in _wrap_create_connection
raise client_error(req.connection_key, exc) from exc
aiohttp.client_exceptions.ClientConnectorError: Cannot connect to host localhost:8080 ssl:default [Connect call failed ('::1', 8080, 0, 0)]

[Psycojoker]

LGTM