RFR: 8067680: (sctp) Possible race initializing native IDs

[Rob McKenna]

This is a fix to a possible race in the current sctp code. In a nutshell 
the conditional only checks that isaCls is not null. However if isaCls 
is set by one thread and that thread is interrupted before setting 
isaCtrID, the interrupting thread will falsely assume that isaCtrID has 
been set.

http://cr.openjdk.java.net/~robm/8067680/webrev.01/
    -Rob