Issues with clearing routers in OSTF tests

When running OSTF tests with Neutron network there are errors appearing in ostf log:

2015-02-06 13:20:53 DEBUG (neutronmanager) Traceback (most recent call last):
  File "/usr/lib/python2.6/site-packages/fuel_health/neutronmanager.py", line 124, in _clear_networks
    cls._remove_router(router, cls.routers[router])
TypeError: unbound method _remove_router() must be called with TestNeutron instance as first argument (got unicode instance instead)

2015-02-06 13:20:53 DEBUG (neutronmanager) Traceback (most recent call last):
  File "/usr/lib/python2.6/site-packages/fuel_health/neutronmanager.py", line 131, in _clear_networks
    cls._remove_subnet(subnet)
TypeError: unbound method _remove_subnet() must be called with TestNeutron instance as first argument (got dict instance instead)

2015-02-06 13:20:53 DEBUG (neutronmanager) Traceback (most recent call last):
  File "/usr/lib/python2.6/site-packages/fuel_health/neutronmanager.py", line 138, in _clear_networks
    cls._remove_network(network)
TypeError: unbound method _remove_network() must be called with TestNeutron instance as first argument (got dict instance instead)

This is because wrong this _clear_network [1] which is a classmethod calls instance methods [2]. This may cause to pollute environment with routers, networks and subntes created in OSTF tests.

[1] https://github.com/stackforge/fuel-ostf/blob/6c046b69d29021524906109f18092363505ee222/fuel_health/neutronmanager.py#L119-L120
[2] https://github.com/stackforge/fuel-ostf/blob/6c046b69d29021524906109f18092363505ee222/fuel_health/neutronmanager.py#L104-L117