PR-1510: LACP timeout, aggregator/actor parameters settable

LACP timeout, aggregator/actor parameters are now settable through XenAPI and
CLI. New bond parameters are lacp-time, lacp-aggregator-key and lacp-actor-key.

Signed-off-by: Mike McClurg <mike.mcclurg@citrix.com>
Refactor Network_utils.Ovs to functorize vsctl commands for testing

Signed-off-by: Mike McClurg <mike.mcclurg@citrix.com>
PR-1510: add unit tests for LACP params setting

Signed-off-by: Mike McClurg <mike.mcclurg@citrix.com>
PR-1510: bond parameters either have defaults or are omitted

Signed-off-by: Mike McClurg <mike.mcclurg@citrix.com>
PR-1510: More test cases

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