8031359: Invocable.getInterface() works incorrectly if interface has default methods
Reviewed-by: attila, hannesw
<test/script/basic/JDK-8012164.js>.error(test/script/basic/JDK-8012164.js:38)
<test/script/basic/JDK-8012164.js>.func(test/script/basic/JDK-8012164.js:33)
<test/script/basic/JDK-8012164.js>.<program>(test/script/basic/JDK-8012164.js:47)