RFR: 8242034 Remove JRE_HOME references

[Erik Gahlin]

Hi,

Could I have a review this small change.

There is no longer a JRE_HOME, so I replaced it with JAVA_HOME. Removing JRE_HOME completely makes it hard to understand where the .jfr-files can be located. JDK_HOME would be an alternative, but JAVA_HOME seemed more appropriate (and more used in other source code).

Webrev:
http://cr.openjdk.java.net/~egahlin/8242034/ <http://cr.openjdk.java.net/~egahlin/8242034/>

Bug:
https://bugs.openjdk.java.net/browse/JDK-8242034

Testing: jdk/jdk/jfr

Thanks
Erik