[urgent] RFR: JDK-8189679: JDK-8189094 broke testing in Mach 5

[Erik Joelsson]

In the change for JDK-8189094 I accidentally broke testing in Mach 5. 
The problem is in jib-profiles.js where the definition of boot_jdk_home 
is no longer defined globally in the common object, and because of this, 
JT_JAVA does not get a good value in the run-test* profiles.

This patch restores common.boot_jdk_home and common.boot_jdk_version. 
Testing is under way.

Webrev: http://cr.openjdk.java.net/~erikj/8189679/webrev.01/

Bug: https://bugs.openjdk.java.net/browse/JDK-8189679

/Erik