fixup: default for lacp-aggregation-key, skip if empty

Signed-off-by: Mike McClurg <mike.mcclurg@citrix.com>
fixup: test case update

Signed-off-by: Mike McClurg <mike.mcclurg@citrix.com>
fixup: lacp-time=slow default

Signed-off-by: Mike McClurg <mike.mcclurg@citrix.com>