Use generate_defaults instead of os_defaults fixed parameters

Use generate_defaults instead of os_defaults fixed parameters

JIRA: FUNCTEST-131

Running generate_defaults.py in prepare_env.sh (before running any test)
will create a file with the CURRENT OpenStack objects in
the deployment. After each test, the cleanup script will take into
consideration those parameters instead of the specified in
os_defaults.yaml

Keep os_defaults.yaml for the moment

Change-Id: I5f38fef47f0a6d79407d1d582b1e7d3713503e07
Signed-off-by: jose.lausuch <jose.lausuch@ericsson.com>
(cherry picked from commit 47635924e6def36be3c44a047d91018e47a439eb)