feat: create subdir if not exists

[andyzhangx]

What type of PR is this?
/kind feature

What this PR does / why we need it:
feat: create subdir if not exists
In original behavior, subDir must exist if it's provided in storage class, this PR would create subdir if not exists

Which issue(s) this PR fixes:

Fixes #

Requirements:

• uses conventional commit messages
• includes documentation
• adds unit tests
• tested upgrade from previous version

Special notes for your reviewer:

Release note:

feat: create subdir if not exists

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: andyzhangx

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• OWNERS [andyzhangx]

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[coveralls]

Pull Request Test Coverage Report for Build 2483674730

• 46 of 48 (95.83%) changed or added relevant lines in 2 files are covered.
• 1 unchanged line in 1 file lost coverage.
• Overall coverage increased (+0.6%) to 85.07%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
pkg/smb/controllerserver.go	36	38	94.74%

Files with Coverage Reduction	New Missed Lines	%
pkg/smb/controllerserver.go	1	82.1%

Totals
Change from base Build 2439455779:	0.6%
Covered Lines:	792
Relevant Lines:	931

---

💛 - Coveralls

[andyzhangx]

/retest

[andyzhangx]

/test pull-csi-driver-smb-e2e-capz
/test pull-csi-driver-smb-e2e-capz-windows-2019

[andyzhangx]

/test pull-csi-driver-smb-external-e2e

[andyzhangx]

/retest

[andyzhangx]

/retest

[k8s-ci-robot]

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

Test name	Commit	Details	Required	Rerun command
pull-csi-driver-smb-e2e-capz	aa4b45b	link	false	/test pull-csi-driver-smb-e2e-capz
pull-csi-driver-smb-e2e-capz-windows-2019	aa4b45b	link	false	/test pull-csi-driver-smb-e2e-capz-windows-2019

Full PR test history. Your PR dashboard. Please help us cut down on flakes by linking to an open issue when you hit one in your PR.

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