Fix flaky integration tests

[efiacor]

The following "integration" tests are very unstable and block PRs due to being run as presubmit jobs.

http://prow.nephio.io/job-history/gs/prow-nephio-sig-release/pr-logs/directory/install-integration

https://prow.nephio.io/job-history/gs/prow-nephio-sig-release/pr-logs/directory/bootstrap-integration

The issue seems to be related to ssh key for the ansible user:

`PLAY [Boostrap servers] ********************************************************

TASK [Gathering Facts] *********************************************************
fatal: [int-focal-vm-bootstrap-918958902]: UNREACHABLE! => {"changed": false, "msg": "Failed to connect to the host via ssh: Warning: Permanently added '35.224.148.255' (ED25519) to the list of known hosts.\r\nroot@35.224.148.255: Permission denied (publickey).", "unreachable": true}`