RFR(XS) 8026698: Incorrect error handling in Metaspace::allocate

[Mikael Gerdin]

Hi all,

Please review this small fix to the caller of report_metadata_oome to use the 
correct exception handling CHECK_NULL instead of passing THREAD and expecting 
the code to not reach the next line.
Even though the current code is equivalent to what I'm proposing it's 
misleading.

Webrev: http://cr.openjdk.java.net/~mgerdin/8026698/webrev.0/
Buglink: https://bugs.openjdk.java.net/browse/JDK-8026698

/Mikael