RFR(trivial): 8233659: [TESTBUG] runtime/cds/appcds/CommandLineFlagCombo.java fails when jfr is disabled

[Jie Fu]

Hi all,

May I get reviews for the one-line change?

JBS:    https://bugs.openjdk.java.net/browse/JDK-8233659
Webrev: http://cr.openjdk.java.net/~jiefu/8233659/webrev.00/

Thanks a lot.
Best regards,
Jie