fix: clean java inner class files in examples

fix: clean java inner class files in examples

Java classes that contain inner classes will result in additional class
files being created when compiled in the form of
'Class$InnerClass.class'. Expand the clean target to delete those
additional files.

Change-Id: I0ed7939dcaefa5ca26db9438f7a9b34e57d78f21
Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>