rptest: clean teleport data dir before use

[andrewhsu]

Fixes https://github.com/redpanda-data/cloudv2/issues/12090

clean teleport data dir before each use so the expired identity is not reused.

verified with simple test:

ducktape \
  --debug \
  --globals=/home/ubuntu/redpanda/tests/globals.json \
  --cluster=ducktape.cluster.json.JsonCluster \
  --cluster-file=/home/ubuntu/redpanda/tests/cluster.json \
  tests/rptest/tests/services_self_test.py::SimpleSelfTest.test_cloud

output:

...
[INFO  - 2024-01-30 05:06:02,510 - kubectl - _setup_tbot - lineno:257]: cleaning teleport data dir
[INFO  - 2024-01-30 05:06:02,511 - kubectl - _setup_tbot - lineno:259]: starting tbot to generate identity
WARN [TBOT]      CLI parameters are overriding onboarding config from  config/config.go:472
INFO [TBOT]      Created directory "/tmp/tbot-data" config/destination_directory.go:132
...
test_id:    rptest.tests.services_self_test.SimpleSelfTest.test_cloud
status:     PASS
run time:   36.092 seconds
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
========================================================================================================================================================================================
SESSION REPORT (ALL TESTS)
ducktape version: 0.8.18
session_id:       2024-01-30--004
run time:         36.110 seconds
tests run:        1
passed:           1
flaky:            0
failed:           0
ignored:          0
opassed:          0
ofailed:          0
========================================================================================================================================================================================

Backports Required

• none - not a bug fix
• none - this is a backport
• none - issue does not exist in previous branches
• none - papercut/not impactful enough to backport
• v23.3.x
• v23.2.x
• v23.1.x

Release Notes

• none

[andrewhsu]

example output in PR description. ready for review.

[travisdowns]

Does this slow down each test?

I.e., is the tbot setup time longer when starting from an empty directory?

[andrewhsu]

Does this slow down each test?

it seems to be negligible, tbot start takes ~5 sec before and after this change

[travisdowns]

Thanks, LGTM and should be a good QoL improvement!