Description of problem: Running the below tempest test on RHOS 16.1 config drive vfat deployment failed:
tempest.scenario.test_stamp_pattern.TestStampPattern.test_stamp_pattern


Version-Release number of selected component (if applicable):
core_puddle: RHOS-16.1-RHEL-8-20200418.n.0

How reproducible: always


Steps to Reproduce:
1. Deploy RHOS 16.1 with config drive vfat
2. Run the following tempest test: tempest.scenario.test_stamp_pattern.TestStampPattern.test_stamp_pattern
3. Tempest test fails 

Actual results:


Traceback (most recent call last):
  File "/usr/lib/python3.6/site-packages/tempest/common/utils/__init__.py", line 89, in wrapper
    return f(*func_args, **func_kwargs)
  File "/usr/lib/python3.6/site-packages/tempest/scenario/test_stamp_pattern.py", line 142, in test_stamp_pattern
    server=server_from_snapshot)
  File "/usr/lib/python3.6/site-packages/tempest/scenario/manager.py", line 775, in get_timestamp
    % mount_path)
  File "/usr/lib/python3.6/site-packages/tempest/lib/common/utils/linux/remote_client.py", line 33, in wrapper
    return function(self, *args, **kwargs)
  File "/usr/lib/python3.6/site-packages/tempest/lib/common/utils/linux/remote_client.py", line 108, in exec_command
    return self.ssh_client.exec_command(cmd)
  File "/usr/lib/python3.6/site-packages/tempest/lib/common/ssh.py", line 204, in exec_command
    stderr=err_data, stdout=out_data)
tempest.lib.exceptions.SSHExecCommandFailed: Command 'set -eu -o pipefail; PATH=$PATH:/sbin:/usr/sbin; sudo cat /mnt/timestamp', exit status: 1, stderr:
cat: can't open '/mnt/timestamp': No such file or directory

stdout:

Expected results:
Test passed

Additional info: