[integ-tests-framework] Fix SSH banner timeout when using bastion gateway in RemoteCommandExecutor

[hanwen-cluster]

Description of changes

The SSH gateway command used for bastion connections was missing -o StrictHostKeyChecking=no and -i {cluster.ssh_key}. When the bastion host key was not in known_hosts, the gateway ssh process would prompt interactively for host key verification. Since paramiko runs this process non-interactively, the prompt blocks stdin indefinitely, preventing the SSH banner from reaching paramiko and causing a paramiko.ssh_exception.SSHException: Error reading SSH protocol banner after the 60-second banner timeout.

This only manifested in environments where ~/.ssh/config did not already set StrictHostKeyChecking no globally. Environments that had this configured (or had the bastion host already in known_hosts) were unaffected.

Tests

The following tests have passed:

{%- import 'common.jinja2' as common with context -%}
{{- common.OSS_COMMERCIAL_X86.append("rocky8") or "" -}}
{{- common.OSS_COMMERCIAL_X86.append("rocky9") or "" -}}
---
test-suites:
  schedulers:
    test_slurm_accounting.py::test_slurm_accounting:
      dimensions:
        - regions: ["ap-south-1"]
          instances:  {{ common.INSTANCES_DEFAULT_X86 }}
          oss: ["alinux2023"]
          schedulers: ["slurm"]
    test_slurm_accounting.py::test_slurm_accounting_external_dbd:
      dimensions:
        - regions: [ "ap-south-1" ]
          instances: {{ common.INSTANCES_DEFAULT_X86 }}
          oss: ["ubuntu2404"]
          schedulers: ["slurm"]

Checklist

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• Check if documentation is impacted by this change.

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