RFR: 8158412: [TESTBUG] TestIHOPErgo and TestStressG1Humongous should not be executed when JFR is enabled

[Michail Chernov]

Hi,

Could I have a reviews for this small fix? The fix adds new custom JTreg 
setting for @requires tag - vm.FlightRecorder. New setting is used in 
all updated tests. Tests will be exclude if JFR is enabled.

https://bugs.openjdk.java.net/browse/JDK-8158412
http://cr.openjdk.java.net/~mchernov/8158412/webrev.root.00/
http://cr.openjdk.java.net/~mchernov/8158412/webrev.hotspot.00/

Testing - RBT.

Thanks,
Michail