app/testpmd: remove port status check from TM command

Currently, testpmd CLI doesn't permit to add leaf and non-leaf node when
port is started. It doesn't work in case of i40e device as DCB
configuration is deleted when port is stopped. Therefore, removes the
port status check before invoking leaf and nonleaf node API in the cli.
If needed, device can add port status check at the driver layer.

Signed-off-by: Jasvinder Singh <jasvinder.singh@intel.com>
Acked-by: Wenzhuo Lu <wenzhuo.lu@intel.com>