Redmine

We used to work with two REDMINE instances, development and tests (the same machine and also the same REDMINE installation).
But now we have upgrade to

Environment:
  Redmine version                          2.2.1.stable
  Ruby version                             1.9.2 (i686-linux)
  Rails version                            3.2.11
  Environment                              development 
  Database adapter                         Mysql2
Redmine plugins:
  redmine_importer                         0.4
  redmine_mylyn_connector                  2.8.2.stable

and when we try to execute

ruby script/rails server webrick -e test -p 4444

=> Booting WEBrick
=> Rails 3.2.11 application starting in test on http://0.0.0.0:4444
=> Call with -d to detach
=> Ctrl-C to shutdown server
A server is already running. Check /redmine/redmine-2.2.1/tmp/pids/server.pid.
Exiting

How can we use the test instance?

NOTE: It works propertly with

Environment:
  Redmine version 2.1.2.stable
  Ruby version 1.8.7 (i686-linux)
  Rails version 3.2.8
  Environment development 
  Database adapter MySQL
Redmine plugins:
  redmine_importer 0.4
  redmine_mylyn_connector 2.8.2.stable