RFR: JDK-8185984: fix a11y and html issues in java.logging module

[Jonathan Gibbons]

Please review a few small changes for accessibility and HTML issue in 
the API docs for the java.logging module.

JBS: https://bugs.openjdk.java.net/browse/JDK-8185984
Webrev: http://cr.openjdk.java.net/~jjg/8185984/webrev.00/

-- Jon