jenkins-library: whitesourceExecuteScan with UnifiedAgent does not honor installArtifacts parameter

When you have a multi-module Maven project with a separate module used as test dependency which you do not want to scan with Whitesource, you cannot exclude it from the scan.

If you use buildDescriptorExcludeList, the following Maven command will be generated: mvn clean install -DskipTests --global-settings settings.xml --projects !<module-to-be-excluded>

This command will fail if the <module-to-be-excluded> is a test dependency in another module. For that issue, we had the whitesourceExecuteScan option installArtifacts. This option was evaluated in the scanMaven.go file but not in the UnifiedAgent version scanUA.go.