Use the default SecureRandom provider.

Don't be tricky when trying to set the seed for the secure
random number generator.  Setting the seed manually eliminates
the internal randomization the SecureRandom class does automatically,
reducing randomness.  Just use the default seed, which is designed
to be safe.

Change-Id: I5747c2b3a10cf04e33d2202195951ed5cb82b2fe