8207830: [aix] disable jfr in build and tests

[Lindenmaier, Goetz]

Hi,

We didn't manage to port JFR to aix in the jdk11 time frame.
Thus I would like to disable it in the build. 
As well, I would like to introduce @requires vm.hasJFR which 
will disable the tests on aix, and also on linuxsparcv9 and zero.

Two webrevs for better readability:
This contains the functional changes
http://cr.openjdk.java.net/~goetz/wr18/8207830-aixDisableJFR/01/
This contains adding @requires. 
http://cr.openjdk.java.net/~goetz/wr18/8207830-aixDisableJFR/01-test/
The only one not straight forward is runtime/appcds/sharedStrings/FlagCombo.java

Best regards,
  Goetz.