Refractored Breakout Mode CLI subcommand with speed fix

[samaity]

Signed-off-by: Sangita Maity sangitamaity0211@gmail.com

- What I did
Refactored the code. Removed a function that is not needed anymore. Speed is now properly populated via portconfig.py

This PR is dependent on portconfig.py file in sonic-buildimage

- How I did it
using portconfig.py in sonic build image.

• How to verify it
  Verified using VS test case mentioned here

samaity@server09:~/REPO_FACTORY/GIT_REPO/DPB/sonic-buildimage/platform/vs/tests/breakout$ sudo pytest -s -v --dvsname=vs-sang test_breakout_cli.py
========================================================================================= test session starts =========================================================================================
platform linux2 -- Python 2.7.15+, pytest-3.3.0, py-1.8.0, pluggy-0.6.0 -- /usr/bin/python
cachedir: .cache
rootdir: /home/samaity/REPO_FACTORY/GIT_REPO/DPB/sonic-buildimage/platform/vs/tests/breakout, inifile:
collected 2 items

test_breakout_cli.py::TestBreakoutCli::test_InitialBreakoutMode remove extra link dummy
PASSED                                                                                      [ 50%]
test_breakout_cli.py::TestBreakoutCli::test_mode_1X100G **** Breakout Cli test Starts ****
**** 1X100G --> 2x50G passed ****
**** 2x50G --> 1x100G[40G] passed ****
**** 1X100G --> 4x25G[10G] passed ****
**** 4x25G[10G] --> 1x100G[40G] passed ****
**** 1x100G[40G] --> 2x25G(2)+1x50G(2) passed ****
**** 2x25G(2)+1x50G(2) --> 1x100G[40G] passed ****
**** 1x100G[40G] --> 1x50G(2)+2x25G(2)  passed ****
**** 1x50G(2)+2x25G(2) --> 1x100G[40G] passed ****
**** 1x100G[40G] --> 2x50G  passed ****
**** 2x50G --> 2x25G(2)+1x50G(2)  passed ****
**** 1x50G(2)+2x25G(2) --> 2x25G(2)+1x50G(2)  passed ****
**** 2x25G(2)+1x50G(2)  --> 1x100G[40G]  passed ****
PASSED                                                                                              [100%]