Support OpenJDK 10 for builder images
Install OpenJDK 10 from http://jdk.java.net/ into /opt.
While the default version of Java will still be 1.8.0 version,
set the slave links using alternatives so that the
required version of Java can be switched during job runtime.
Example: the command switches to Java 10.
$ echo 3 | sudo alternatives --config java
JIRA: https://jira.linuxfoundation.org/browse/RELENG-1299
Change-Id: I54ac0c4913ae7afd173a1edf746d6bd31fb6d74d
Signed-off-by: Anil Belur <abelur@linuxfoundation.org>