Add extra elements check for 'show_volume_type' command

Update "test_volume_type_create_get_delete" testcase to verify
'show_volume_type' command according to the following parameters:
'description', 'is_public' and 'os-volume-type-access:is_public'.

Change-Id: I62e77a89321ca36455de4251b13f916483822da0
1 file changed