jjb: Use alternative log4j classpath on sles 15.4+

jjb: Use alternative log4j classpath on sles 15.4+

A fresh installation of SLES15SP4 doesn't have the symbolic links that
exist on ci-node-sles15sp4, eg. `/usr/share/java/log4j-1.2.jar` ->
`/usr/share/java/log4j12/log4j-12.jar`.

I suspect that the symlinks were installed manually at some point to
simplify the build scripts. As the complexity is already added to
support SLES15SP5 from fresh installations, the proper locations for
log412 can be used on SLES15SP4 as well.

Change-Id: Id2747abd029a4b4978dd6f0214f5ed3ab1bb267c
Signed-off-by: Kienan Stewart <kstewart@efficios.com>