22406: Install arvados-server on test nodes during build

22406: Install arvados-server on test nodes during build

See comments for rationale. `arvados-server install` runs database setup
Rake tasks, which require `arvados-server` to be on $PATH to load
configuration.

We should probably stop doing that and just let `run-tests.sh` do the
database setup since it needs to anyway. That can happen as part of
migrating this Jenkins job to use the test environment Ansible playbook.

Arvados-DCO-1.1-Signed-off-by: Brett Smith <brett.smith@curii.com>