Possible merging "fedcloud openstack" and "fedcloud openstack-int"

[tdviet]

fedcloud openstack-int, the interactive OpenStack command seems neglected. It would be better to merge the command into the fedcloud openstack as follows:

• adding option --interactive or --int for interactive mode for fedcloud openstack command. Some OpenStack commands, e.g. openstack ssh need interactive mode for accessing standard input
• if fedcloud openstack command is executed without OpenStack command, i.e. fedcloud openstack --site site --vo vo, the interactive mode will be activated automatically, so users can enter OpenStack commands