RFR(T/XS): 8225509: clean_catch_blocks must add preds first

[Nils Eliasson]

Hi,

When the late load barrier insertion is handling loads in 
clean_catch_blocks, the pushing of predecessor nodes on the iteration 
stack must be done before the processing of a load, because it changes 
the graph.

Bug: https://bugs.openjdk.java.net/browse/JDK-8225509

Webrev: http://cr.openjdk.java.net/~neliasso/8225509/webrev.01/

Please review,

Nils