Restore metal3-dev-env only if it exists

[elfosardo]

If the metal3-dev-env dir does not exist for some reason (it was removed before, or changed location before the cleanup), the clenaup will fail.
Restore it only if the dir exists.

[openshift-ci]

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[elfosardo]

/retest

[elfosardo]

/retest

[elfosardo]

/retest

[openshift-ci]

@elfosardo: 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-metal-ipi-serial-ovn-ipv6	8f209fe	link	false	/test e2e-metal-ipi-serial-ovn-ipv6

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