[DOC] Fix to make sure the command allows interaction (#562)

Author: AvnerCohen

docs/otp.md

@@ -23,7 +23,7 @@ In order to enable two factor authentication the following steps are required.
 
 * Generate authentication configuration for your client. -t is needed to show QR code, -i is optional for interactive usage
 
-        docker run -v $OVPN_DATA:/etc/openvpn --rm -t kylemanna/openvpn ovpn_otp_user <user>
+        docker run -v $OVPN_DATA:/etc/openvpn --rm -it kylemanna/openvpn ovpn_otp_user <user>
 
 The last step will generate OTP configuration for the provided user with the following options