nova-manage cmd improvement

- Allow to pass print format-type to nova-manage cmd
  As of now, the default output of nova-manage is printed in table format, which is not ideal to pass into another program as input.
  We ofthen has to use different shell tools to aling the output, for example nova-manage cell_v2 list_cells.
for example to get the cell_uuid, we have to use something like
  `cell_uuid=$(nova-manage cell_v2 list_cells | tr ' ' '|' | tr --squeeze-repeats '|' | grep -e "^|$CELL_NAME|" | cut -d '|' -f 3`

  The propsed change is to have --format (-f) option which user can pass to nova-manage cmd, and print output in other formats too, for example
  json, csv. This helps to extract the data easily for the nova-manage cmd output.
  The default output format will still be a tabular format for backward compability.

- Allow nova-manage cell_v2 to take cell uuid as an option
  This will help to perform operation as per specific cell related operations like cell update and delete.
for more info: https://issues.redhat.com/browse/OSPRH-10284