vault-java-driver: SslConfig silently disables requested TLS verification

vault-java-driver, a Java client for HashiCorp Vault, silently disables TLS certificate and hostname verification in three states where the caller asked for verification: an SslConfig passed to VaultConfig without calling build(), an SslConfig restored by Java deserialization, and VAULT_SSL_VERIFY set to a truthy value other than "true", such as 1, yes or on. In each case SslConfig.isVerify() returns false and the driver installs a trust-all SSLContext. An attacker on the network path to the Vault server can then read the Vault token and secrets in transit and forge responses. This issue affects io.github.jopenlibs:vault-java-driver 5.2.0 through 6.2.3. It is fixed in 7.0.0.