DLPX-87656 Enable SFTP for Internal Variants

[dbshah12]

Problem

• As part of https://github.com/delphix/dlpx-app-gate/pull/1190 of dlpx-app-gate, the file transfer protocol of sshj changed from SCP to SFTP but sftp is disabled on DE so to test SFTP working on DE as part of dxoTest and internal-variants uncomment below line from sshd_config:
  Subsystem sftp /usr/lib/openssh/sftp-server

Solution

• Added a condition in the ansible code of commenting above the line, Only comment for the external variants.

Testing

• Took ab-pre-push image and tested sftp, sftp is working on the qa-internal image.