RFR: 8169335: Add a crypto.policy fallback in case Security Property 'crypto.policy' does not exist

[Bradford Wetmore]

Simple codereview:

     http://cr.openjdk.java.net/~wetmore/8169335/webrev.00

The "crypto.policy" Security property is normally defined/configured in 
the java.security file at build time.  (e.g. "limited" or "unlimited") 
Rather than currently failing catastrophically if this value doesn't 
exist, there should be a sensible default if it is undeclared for 
whatever reason.  We will use a sane fallback value of "limited".

If the distribution has also removed the "limited" policy directory then 
the VM will still fail to initialize, but we have at least made an 
effort to recover.

Thanks,

Brad