Document the HELM_TLS_HOSTNAME environment variable in 'helm --help'

Resolves #5120
Also adjust order `ENABLE` -> `VERIFY` -> `HOSTNAME`

Signed-off-by: Aaron Roydhouse <aaron@roydhouse.com>

cmd/helm/helm.go

@@ -69,8 +69,9 @@ Environment:
   $HELM_TLS_CA_CERT    path to TLS CA certificate used to verify the Helm client and Tiller server certificates (default "$HELM_HOME/ca.pem")
   $HELM_TLS_CERT       path to TLS client certificate file for authenticating to Tiller (default "$HELM_HOME/cert.pem")
   $HELM_TLS_KEY        path to TLS client key file for authenticating to Tiller (default "$HELM_HOME/key.pem")
-  $HELM_TLS_VERIFY     enable TLS connection between Helm and Tiller and verify Tiller server certificate (default "false")
   $HELM_TLS_ENABLE     enable TLS connection between Helm and Tiller (default "false")
+  $HELM_TLS_VERIFY     enable TLS connection between Helm and Tiller and verify Tiller server certificate (default "false")
+  $HELM_TLS_HOSTNAME   the hostname or IP address used to verify the Tiller server certificate (default "127.0.0.1")
   $HELM_KEY_PASSPHRASE set HELM_KEY_PASSPHRASE to the passphrase of your PGP private key. If set, you will not be prompted for
                        the passphrase while signing helm charts