flow: handle flow error return messages

Now we have multiple flow update strategies we use
NET_FLOW_FLOWS_ERROR_CONT_LOG for the CLI. This
will try to program all flow messages and then
return a list of any failures.

We can only program one flow at a time anyways
but future feature to read in from file.

Signed-off-by: John Fastabend <john.r.fastabend@intel.com>