Testing Done: tested master and 2.5_br images with testifupdown2 suite and hand tested
This patch creates a json defaults file upon bootup
(which can be overridden by customer configs in /etc)
which the ethtool module in ifupdown2 will consult
when "link-x" configs are removed in order to restore
them to the initial settings used by the switch.
(cherry picked from commit 8388664f5a5a85f2a813cafbf40ac92d7b86f4bf)
Conflicts:
packages/cl-utilities/dist-packages/cumulus/portconfig.py
packages/cl-utilities/usrlib/update-ports
tests/tests/smoke/testifupdown2.py
