Preserving Nova instances from os_defaults.yaml
Preserving Nova instances from os_defaults.yaml

Previously clean_openstack deleted all the existing instances
even if they were included into os_defaults.yaml.

Change-Id: Id7c17ec86a5616c44bd2965844a4a8545054358b
Signed-off-by: vitikkan <478f7ca616a7d23ed1ae94747b74c4df3ef9bdf3@nokia.com>

opnfv/functest,mywulin/functest,mywulin/functest,opnfv/functest