RFR: 8154791: Xlog classload too redundant msgs info/debug

[Rachel Protacio]

Hello!

Please review this enhancement correcting redundancies and neatening up 
the -Xlog:class+load code. The redundancy in the code before I believe 
stemmed from a misunderstanding about logging levels (the comment saying 
they are not mutually exclusive was misleading).

Tested with JPRT and RBT.

Bug: https://bugs.openjdk.java.net/browse/JDK-8154791
Webrev: http://cr.openjdk.java.net/~rprotacio/8154791.00

Thanks,
Rachel