RemoveAssociation return false when there is multiple extensions with same mime type.

Steps to reproduce:
Create a JNLP file with following entry.
<association extensions="abc" mime-type="x-application/abc"/>
<association extensions="xyz" mime-type="x-application/abc"/>
Invoke removeAssociation.
        String mime = "x-application/abc";
        String [] exts = {"abc","xyz"};
        boolean result = is.removeAssociation(mime,exts);
Expected to return true but returned false.

TestCase: http://jdeploy01.india.sun.com:8080/JavawsMustangIntegTest/integrationService/RemoveMultipleAssociation.jnlp