JDK-8069149: jdk.internal.pref.Perf is unaware of the VM option UsePerfData

[Gary Adams]

A patch was done previously to prevent an error when -XX:-UsePerfData
is used, but this bug was filed to make the setting more visible in the
jdk.internal.perf package.

    Webrev: http://cr.openjdk.java.net/~gadams/8069149/webrev.00/
    Issue: https://bugs.openjdk.java.net/browse/JDK-8069149

I have tried a few initial tests using:

    make run-tests \
          TEST_OPTS=VM_OPTIONS=-XX:-UsePerfData \
          TEST=open/test/jdk/sun/management/jmxremote

While I'm tracking down one test timeout,  I'd like to get some
feedback on the approach used here :

    - the basic mechanism propagates the "is initialized" state up to 
Perf.java;
       does the state need to be exposed to users getPerf(), or is it 
sufficient
       to provide exceptions at this level.
    - an existing use of IOException was used in the case of attach 
failures;
       added IOExceptions to the createXXX methods if the memory was not 
initialized
    - presuming a CSR would be needed to cover the IOExceptions
    - it appears that jdk.internal.perf has very limited usage,
       is it still needed/used (?)

Any feedback appreciated.