Trim user id before adding to docker run command

[cherylking]

For internally reported issue with running devc on LMP 3.10.1. The same scenario worked on LMP 3.10. The error reported was:

[ERROR] Failed to execute goal io.openliberty.tools:liberty-maven-plugin:3.10.1:devc (default-cli) on project guide-testcontainers: Error starting the server in dev mode.: An error occurred while running the container: docker: Error response from daemon: unable to find user 0 : no matching entries in passwd file. RC=125 -> [Help 1]

There seems to be a trailing space for the --user 0 on the docker run command. The changes made in this PR causes this space to be preserved, whereas it would have been trimmed previously.