Create missing mount points when tuning nodes

[tnozicka]

Description of your changes:
On GKE the nodetuning was failing because of a missing mount. X-mount.mkdir makes sure it's always there.

[scylla-operator-bot]

@tnozicka: The following test failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
ci/prow/e2e-gke	279c4d7	link	true	/test e2e-gke

Full PR test history. Your PR dashboard.

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[tnozicka]

https://github.com/scylladb/scylla-operator/actions/runs/5899796911/job/16003016773#step:3:3042

Summarizing 1 Failure:
  [FAIL] ScyllaCluster should replace a node [It] using HostID based procedure when version of ScyllaDB is "docker.io/scylladb/scylla:5.2.0"
  github.com/scylladb/scylla-operator/test/e2e/set/scyllacluster/verify.go:277

Ran 22 of 30 Specs in 2598.992 seconds
FAIL! -- 21 Passed | 1 Failed | 1 Pending | 7 Skipped

e2e-parallel fails the same way on master
https://github.com/scylladb/scylla-operator/actions/runs/5896785627/job/15995395176#step:3:4504

e2e-parallel with alpha fails the same way plus monitoring flake

Summarizing 2 Failures:
  [FAIL] ScyllaDBMonitoring [It] should setup monitoring stack
  github.com/scylladb/scylla-operator/test/e2e/set/scylladbmonitoring/scylladbmonitoring.go:180
  [FAIL] ScyllaCluster should replace a node [It] using HostID based procedure when version of ScyllaDB is "docker.io/scylladb/scylla:5.2.0"
  github.com/scylladb/scylla-operator/test/e2e/set/scyllacluster/verify.go:277

Ran 24 of 30 Specs in 2491.639 seconds
FAIL! -- 22 Passed | 2 Failed | 1 Pending | 5 Skipped

none of them seem connected to the change done here

[zimnx]

/lgtm

[scylla-operator-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: tnozicka, zimnx

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