RFR (JAXP) 8176405 : Catalog circular reference check did not work in certain scenarios

[huizhe wang]

Hi,

Please review a fix to the circular reference check that incorrectly 
treated duplicate entries as circular.

JBS: https://bugs.openjdk.java.net/browse/JDK-8176405
Webrev: http://cr.openjdk.java.net/~joehw/jdk9/8176405/webrev/

Thanks,
Joe