update MountEntry.Type to plugin name on mount tune for mounts created in Vault pre-v1.0.0

[thyton]

Description

This PR fixes MountEntry.Type of mounts that were created in Vault pre-v1.0.0 on mount tune after Vault upgraded to post-v1.0.0. On mount tune with plugin_version, if MountEntry.Type has "plugin" value and MountEntry.Config.PluginName has a different value, MountEntry.Type is updated to match.

# vault_0.11.6
root@6fa90bb39cbf:/VAULT-21999/vault_0.11.6_linux_arm64# ./vault secrets enable -path=my-secret -plugin-name=venafi-pki-backend plugin
Success! Enabled the venafi-pki-backend plugin at: my-secret/

root@6fa90bb39cbf:/VAULT-21999/vault_0.11.6_linux_arm64# ./vault secrets list --format=json
{
...
  "my-secret/": {
    "type": "plugin",
    "description": "",
    "accessor": "plugin_af8cf934",
    "config": {
      "default_lease_ttl": 0,
      "max_lease_ttl": 0,
      "force_no_cache": false,
      "plugin_name": "venafi-pki-backend"
    },
    "options": null,
    "local": false,
    "seal_wrap": false
  },
...
 }

# Upgrade to vault 1.18

# Then, register the versioned plugin
root@6fa90bb39cbf:/VAULT-21999/vault_1.18_linux_arm64# ./vault plugin register     -sha256=4b0772e97428e6e18867877d572262704fdd7ee65e5d1dc8d20c2b859f2d18a2     -command=venafi-pki-backend -version=v1.0.0 secret venafi-pki-backend
Success! Registered plugin: venafi-pki-backend

root@6fa90bb39cbf:/VAULT-21999/vault_1.18_linux_arm64# ./vault plugin list --format=json
...
    {
      "type": "secret",
      "name": "venafi-pki-backend",
      "builtin": false
    },
    {
      "type": "secret",
      "name": "venafi-pki-backend",
      "version": "v1.0.0",
      "builtin": false
    }
  ],
...

# Then, tune the secret mount
root@6fa90bb39cbf:/VAULT-21999/vault_1.18_linux_arm64# ./vault secrets tune -plugin-version="v1.0.0" my-secret/
Success! Tuned the secrets engine at: my-secret/

# We still have to reload the plugin so the running version reflects what was tuned
root@6fa90bb39cbf:/VAULT-21999/vault_1.18_linux_arm64# ./vault secrets list --format=json
...
"my-secret/": {
    "uuid": "30991468-57e8-8334-d7da-664ad3a29de6",
    "type": "venafi-pki-backend",
    "description": "",
    "accessor": "plugin_af8cf934",
    "config": {
      "default_lease_ttl": 0,
      "max_lease_ttl": 0,
      "force_no_cache": false
    },
    "options": null,
    "local": false,
    "seal_wrap": false,
    "external_entropy_access": false,
    "plugin_version": "v1.0.0",
    "running_plugin_version": "v1.18.0+builtin.vault",
    "running_sha256": "",
    "deprecation_status": ""
  },
...

# Reload the plugin
root@6fa90bb39cbf:/VAULT-21999/vault_1.13.7+ent_linux_arm64# ./vault plugin reload -plugin venafi-pki-backend
Success! Reloaded plugin: venafi-pki-backend

# Now, the running version should be v1.0.0
root@6fa90bb39cbf:/VAULT-21999/vault_1.18_linux_arm64# ./vault secrets list --format=json
...
"my-secret/": {
    "uuid": "30991468-57e8-8334-d7da-664ad3a29de6",
    "type": "venafi-pki-backend",
    "description": "",
    "accessor": "plugin_af8cf934",
    "config": {
      "default_lease_ttl": 0,
      "max_lease_ttl": 0,
      "force_no_cache": false
    },
    "options": null,
    "local": false,
    "seal_wrap": false,
    "external_entropy_access": false,
    "plugin_version": "v1.0.0",
    "running_plugin_version": "v1.0.0",
    "running_sha256": "4b0772e97428e6e18867877d572262704fdd7ee65e5d1dc8d20c2b859f2d18a2",
    "deprecation_status": ""
  },
...

TODO only if you're a HashiCorp employee

• Labels: If this PR is the CE portion of an ENT change, and that ENT change is
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• Labels: If this PR is a CE only change, it can only be backported to N, so use
  the normal backport/x.x.x label (there should be only 1).
• ENT Breakage: If this PR either 1) removes a public function OR 2) changes the signature
  of a public function, even if that change is in a CE file, double check that
  applying the patch for this PR to the ENT repo and running tests doesn't
  break any tests. Sometimes ENT only tests rely on public functions in CE
  files.
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  description. Also, make sure the changelog is in this PR, not in your ENT PR.

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CI Results:
All Go tests succeeded! ✅

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All builds succeeded! ✅

[fairclothjm]

LGTM!