[System tests] Fix file creation in collect packages decorator

[Andrey Sledzinskiy]

 https://github.com/stackforge/fuel-qa/blob/808765cf2a58c02ef361eea65c653b9ac92096c8/fuelweb_test/helpers/utils.py#L141
need to change 'r+' on 'w+'

Traceback (most recent call last):
  File "/home/jenkins/venv-nailgun-tests-2.9/local/lib/python2.7/site-packages/proboscis/case.py", line 296, in testng_method_mistake_capture_func
    compatability.capture_type_error(s_func)
  File "/home/jenkins/venv-nailgun-tests-2.9/local/lib/python2.7/site-packages/proboscis/compatability/exceptions_2_6.py", line 27, in capture_type_error
    func()
  File "/home/jenkins/venv-nailgun-tests-2.9/local/lib/python2.7/site-packages/proboscis/case.py", line 350, in func
    func(test_case.state.get_state())
  File "/home/jenkins/workspace/6.1.centos.bvt_1/fuelweb_test/helpers/decorators.py", line 67, in wrapper
    return func(*args, **kwargs)
  File "/home/jenkins/workspace/6.1.centos.bvt_1/fuelweb_test/tests/test_ha.py", line 82, in deploy_ha_vlan
    self.fuel_web.deploy_cluster_wait(cluster_id)
  File "/home/jenkins/workspace/6.1.centos.bvt_1/fuelweb_test/helpers/decorators.py", line 310, in wrapper
    store_packages_json(environment)
  File "/home/jenkins/workspace/6.1.centos.bvt_1/fuelweb_test/__init__.py", line 48, in wrapped
    result = func(*args, **kwargs)
  File "/home/jenkins/workspace/6.1.centos.bvt_1/fuelweb_test/helpers/utils.py", line 141, in store_packages_json
    settings.LOGS_DIR), 'r+') as outfile:
IOError: [Errno 2] No such file or directory: '/home/jenkins/workspace/6.1.centos.bvt_1/logs/packages.json'

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/171611

[Andrey Sledzinskiy (asledzinskiy)]

Fixed by revert https://review.openstack.org/#/c/171633/