Allows deletion of multiple servers through CLI
Allows deletion of multiple servers through CLI

Adds nargs to argparse for delete command to allow
multiple (optional) positional server argument. This
allows users to delete multiple servers using nova delete.
For example:
nova delete xxx yyy aaa zzz will delete valid servers
xxx, yyy and zzz and print exception msg for invalid
delete of server aaa.

Fixes bug892061

Change-Id: I2abe6329e489bfbd3e5ae699e97ef098b38c4537

ntt-sic/python-novaclient,JioCloud/python-novaclient,mat128/python-novaclient,takeshineshiro/python-novaclient,mat128/python-novaclient,citrix-openstack-build/python-novaclient,metacloud/python-novaclient,guptaankita/python-novaclient,CCI-MOC/python-novaclient,Shihta/python-novaclient,akash1808/python-novaclient,guptaankita/python-novaclient,JioCloud/python-novaclient,CCI-MOC/python-novaclient,citrix-openstack-build/python-novaclient,ntt-sic/python-novaclient,Shihta/python-novaclient,metacloud/python-novaclient,takeshineshiro/python-novaclient,akash1808/python-novaclient