[WIP] Improve Tarmak Terraform provider

[dippynark]

What this PR does / why we need it:

• Fail quickly by checking bastion instance exists when using bastion_instance_status data source
• Only create vault init tokens on create operations (no read or delete) with the vault_instance_role resource

Which issue this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close that issue when PR gets merged): fixes #358

Release note:

[jetstack-bot]

@dippynark: Adding the "do-not-merge/release-note-label-needed" label because no release-note block was detected, please follow our release note process to remove it.

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[jetstack-bot]

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[dippynark]

hashicorp/terraform#17034

[jetstack-bot]

@dippynark: PR needs rebase.

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[jetstack-bot]

@dippynark: The following tests failed, say /retest to rerun them all:

Test name	Commit	Details	Rerun command
tarmak-quick-verify	a49d142	link	/test verify quick
tarmak-puppet-module-tarmak-acceptance-1-14-centos	a49d142	link	/test puppet-tarmak-acceptance-centos v1.14

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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