* [python] - issue #1172 - add version switching mechanism using update-alternatives

* removed commented code

* [python] - update-alternatives addition for ease in switching of python versions - complete

* changes for passing of other tests !!

* change for better positioning of code

* Added test case scenario for Update-Alternatives check

* added scenario for testing

* [alternatives] - added option for fedora, centos & rhel

* changed file name

* changes for update-alternatives test case proper functioning

* arrange in asc order for default value retention after testing ends