nm-device now applies ethtool coalesce settings during stage 2 "device
config" of the connection activation.

Coalesce settings will be then restored (according to what the state
was before the connection got activated on the device) when the
connection is deactivated during the device cleanup.

One thing to be noted is that unset coalesce settings (in the profile)
will not be touched at all by NetworkManager so that if the NIC driver
sets some default values these will be preserved unless specifically
overridden by the connection profile.

https://bugzilla.redhat.com/show_bug.cgi?id=1614700