Add test mode to datacentre

[hawesie]

The datacentre will also need a test mode where it creates its own local directory for storage, rather than assuming a global one. Needed due to #75.

[hawesie]

Also needs randomised or otherwise unique port.

These both must support parallel running of multiple datacentres.

[marc-hanheide]

So... it works nicely in hydro now, but still fails in indigo: http://lcas.lincoln.ac.uk/jenkins/job/devel-indigo-mongodb_store/ARCH_PARAM=amd64,UBUNTU_PARAM=trusty,label=devel/8/console

[marc-hanheide]

Here's the relevant bit:

[INFO] [WallTime: 1410525535.414389] Mongo server address: localhost:58430
Traceback (most recent call last):
  File "/tmp/test_repositories/src_repository/mongodb_store/mongodb_store/scripts/mongodb_server.py", line 166, in <module>
    server = MongoServer()
  File "/tmp/test_repositories/src_repository/mongodb_store/mongodb_store/scripts/mongodb_server.py", line 79, in __init__
    mongov = subprocess.check_output(["mongod","--version"])
  File "/usr/lib/python2.7/subprocess.py", line 566, in check_output
    process = Popen(stdout=PIPE, *popenargs, **kwargs)
  File "/usr/lib/python2.7/subprocess.py", line 710, in __init__
    errread, errwrite)
  File "/usr/lib/python2.7/subprocess.py", line 1327, in _execute_child
    raise child_exception
OSError: [Errno 2] No such file or directory

apparently mongod would need to listed in the package.xml as a dependency as it is not installed here.

[marc-hanheide]

Fixed in #89