Move ShimServiceProvider file re-init/truncate (#5599)

This PR closes #5596 by moving truncate close to when shim service file
concatentation is about to generate a new list. 

The empty file for ShimServiceProvider created during init-properties is not populated via
concat in the conventional jar path, later overwriting the original file
from the aggregator jar. it's also bad practice to have side effects
while still initializing properties. This PR corrects these issues.

Signed-off-by: Gera Shegalov <gera@apache.org>

dist/maven-antrun/build-parallel-worlds.xml

@@ -61,7 +61,6 @@
         <property name="shimServiceRsrc" value="META-INF/services/com.nvidia.spark.rapids.SparkShimServiceProvider"/>
         <property name="shimServiceFile" value="${project.build.directory}/extra-resources/${shimServiceRsrc}"/>
         <property name="aggregatorPrefix" value="${project.build.directory}/deps/${aggregatorArtifact}-${project.version}"/>
-        <truncate file="${shimServiceFile}" create="true" mkdirs="true"/>
         <property name="aggregatorBuildDir" value="${project.basedir}/../aggregator/target"/>
 
         <condition property="should.build.conventional.jar">
@@ -148,6 +147,7 @@
             </sequential>
         </ac:for>
 
+        <truncate file="${shimServiceFile}" create="true" mkdirs="true"/>
         <concat destfile="${shimServiceFile}">
             <fileset dir="${project.build.directory}/parallel-world" includes="spark*/${shimServiceRsrc}"/>
         </concat>