nexus: Move persistent data

When any configuration is done to the nexus server is persists that data
to the sonatype-work directory. Also all maven artifacts are downloaded
into that directory too. So if you want to have that same setup after
upgrading, the sonatype-work directory needs to be somewhere common all
versions. This commit patches nexus to look for that data in var/nexus.

Closes #19361.

Signed-off-by: Adam Vandenberg <flangy@gmail.com>