Bump kernel ethtool get/set wait to 20 + ifupdown2 convert ethtool

Bump kernel ethtool get/set wait to 20 + ifupdown2 convert ethtool
errors to warns

Ticket: CM-3159
Reviewed By: briefly ran this by jtoppins and andy (sfeldma is on
vacation this week).
Testing Done: tested ifupdown2 with ethtool config during boot (sam will
also be adding the testcase mentioned in the bug to ifupdown2 smoke)

The kernel timeout increase helps right now.
we should revisit this again in 2.3 to close all corner cases.

ifupdown2 will now warn on ethtool errors and will also return
non-zero exit status