"veyron.js/src/nacl":  Write private key to config.
"veyron.js/src/nacl":  Write private key to config.

In order to start using the new security model, this CL
modifies the config for WSPR_NACL to write out only
the private key from the directory specified in the
VEYRON_CREDENTIALS env variable.

See also: https://veyron-review.googlesource.com/#/c/5991/

Change-Id: Ie1ced4b2b3696e7b43014b8a4e838a05b3b114a4

vanadium/js,vanadium/js,vanadium/js,vanadium/js