Describe the bug

Users of the pluginUtility are having problems with the generation of plugin configuration files. When the user generates a plugin configuration for a cluster, the first generation works well, but subsequent generations do not work, they seem to cache data from previous generations.

This issue seems to rise from PluginMergeToolImpl.java. In one of the changes, the attributes defined in the class have been changed to static, which may have caused the issue.The PR which addresses these change is 24627.

Steps to Reproduce

The start situation is a newly started controller with wlp version wlp_24_0_0_4.

Then I generate the file for cluster pom, this gives me a correct generated file pom-plugin-cfg1.xml
pluginUtility generate --server=was:******@hostName:Port --cluster=pom --targetPath=/tmp

After that I want to generate a file for a different cluster: qom and I get this file: qom-plugin-cfg.xml
You will notice that this file also includes the server information of the previous run (of cluster pom)
pluginUtility generate --server=was:******@hostName:Port --cluster=qom --targetPath=/tmp

Lastly I generate the file for the original cluster again: pom , now I get this file: pom-plugin-cfg2.xml
You will notice that this includes the servers of cluster pom two times.
pluginUtility generate --server=was:******@hostName:Port --cluster=pom --targetPath=/tmp

Expected behavior
We expect for the pluginUtility tool to generate the plugin-cfg.xml not carrying data from prior runs.

Diagnostic information:

• OpenLiberty Version: wlp_24_0_0_4
• Affected feature(s) pluginUtility
• Java Version: Java 11
• server.xml configuration (WITHOUT sensitive information like passwords)
• If it would be useful, upload the messages.log file found in $WLP_OUTPUT_DIR/messages.log

Additional context
Add any other context about the problem here.