Update docker container URL to serve Jenkins from "subdirectory"

[Josh Davidson]

I migrated a bitnami Jenkins installation to the official docker container and have things running.  One of the issues I'm running into is that the bitnami installation published Jenkins at "https://<server>:<port>/jenkins" and the docker container is just "https://<server>:<port>" (no /jenkins).  Is there something I can set in my docker run command to add the "/jenkins" or failing that, a docker exec I can ran post launch?  Do many things are depending on the old URL for me to leave as-is.

[Josh Davidson]

I was able to get it working by adding --env="JENKINS_OPTS=--prefix=/jenkins" to the docker run command.