fingerprint: add support for fingerprinting multiple Vault clusters (#18253)

Add fingerprinting we'll need to accept multiple Vault clusters in upcoming
Nomad Enterprise features. The fingerprinter will create a map of Vault clients
by cluster name. In Nomad CE, all but the default cluster will be ignored and
there will be no visible behavior change.

testutil/vault.go

@@ -72,6 +72,7 @@ func NewTestVaultFromPath(t testing.T, binary string) *TestVault {
 		RootToken: token,
 		Client:    client,
 		Config: &config.VaultConfig{
+			Name:    "default",
 			Enabled: &enable,
 			Token:   token,
 			Addr:    http,