It is unlikely that we will create a non-unique storage ID
for the following reasons:
a) SecureRandom is a cryptographically strong random number generator
b) IP addresses will likely differ on different hosts
c) DataNode xfer ports will differ on the same host
d) StorageIDs will likely be generated at different times (in ms)
A conflict requires that all four conditions are violated.
NB: The format of this string can be changed in the future without
requiring that old SotrageIDs be updated.