fix: Java examples CLASSPATH override

fix: Java examples CLASSPATH override

Variables provided to make as arguments, called 'command variables' can't
be reassigned a new value in the Makefile. Since the CLASSPATH is now
passed this way in the glue between automake and the example makefiles,
use different names for the internal variables.

Change-Id: Id6289273f211f544a66d933a96f06df75243415f
Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>