RFR: 8210235: JvmtiTrace::safe_get_current_thread_name is unsafe in debug builds

[coleen.phillimore at oracle.com]

Looks good and trivial.
Coleen

On 8/30/18 3:24 PM, Kim Barrett wrote:
> Please review this trivial change to avoid a possible assert, by
> calling Thread::current_or_null rather than Thread::current in a
> context where the NULL case is explicitly handled.
>
> CR:
> https://bugs.openjdk.java.net/browse/JDK-8210235
>
> Webrev:
> http://cr.openjdk.java.net/~kbarrett/8210235/open.00/
>
> Testing:
> Locally (linux-64) verified change builds and ran some tests for
> smoke.  I couldn't find any tests involving TraceJVMTI.
>