8244497: [TESTBUG] Incompatible types conversion error in vmTestbase/vm/runtime/defmeth/StressTest.java after JDK-8243432

[jiefu(傅杰)]

Hi all,

May I get reviews for this fix?

JBS:    https://bugs.openjdk.java.net/browse/JDK-8244497
Webrev: http://cr.openjdk.java.net/~jiefu/8244497/webrev.00/

Testing:
- make test TEST="vmTestbase/vm/runtime/defmeth" CONF=server-release on macos

Thanks a lot.
Best regards,
Jie