PUBDEV-4940 - fix image build for python installation: use get-pip.py script for all pythons instead of easy_install approach.
PUBDEV-4940 - fix image build for python installation: use get-pip.py script for all pythons instead of easy_install approach.

The easy_install approach ends with "package pip not found" error. Using of get-pip.py script is official supported method for pip intallation by https://pip.pypa.io/en/stable/installation/.
It is possible that in the future we will need to adjust this lines for some python version. Currently only python 3.5 need special treath.

h2oai/h2o-3,h2oai/h2o-3,h2oai/h2o-3,h2oai/h2o-3,h2oai/h2o-3,h2oai/h2o-3,h2oai/h2o-3,h2oai/h2o-3