Review request for 8026027: Level.parse should return the custom Level instance instead of the mirrored Level

[Mandy Chung]

This fixes Level.parse to return the custom Level instance.

Webrev at:
http://cr.openjdk.java.net/~mchung/jdk8/webrevs/8026027/webrev.00/

When a custom Level is created, a mirrored level instance (containing 
the same value as the custom Level) is created and used by the logging 
implementation.  Only the custom level should be added to the known 
level list from which Level.parse will look up.

Thanks
Mandy