RFR [XS] 8207832 - ClhsdbCDSCore.java failed with "Couldn't find core file location"

[Ioi Lam]

Please review this simple fix.

     https://bugs.openjdk.java.net/browse/JDK-8207832
http://cr.openjdk.java.net/~iklam/jdk12/8207832_ClhsdbCDSCore_file_location.v01/

On Linux, the core file location can be controlled via 
/proc/sys/kernel/core_pattern.
It could have various patterns such as

    core
    core.%p
    core.%p.something
    /tmp/core
    /tmp/core.%p
    /tmp/core.%p.something

I've tested the fix with all the above patterns, and the %p is correctly
replaced by the process ID.

Note that the pattern can also be more complex, starting with a piping 
character ("|").
I have not touched that part of the code, since it doesn't seem to 
affect our internal
test infrastructure.

I also instrumented ClhsdbCDSCore.java so we can more easily diagnose 
such problems
in the future.

For more info, see 
https://www.kernel.org/doc/Documentation/sysctl/kernel.txt

I'll validate with hs tiers 1/2/3/4.

Thanks
- Ioi