bonding: Add support for probing the bonding module with parameters

Until support for bonding params is added to networkd, this will be
neccessary in order to use bonding parameters (i.e. miimon, mode).
This also makes it such that the 8012q module will only be loaded if
the network config makes use of VLANs.
networkd: Create config directory before writing config
networkd: Restart networkd twice to work around race

https://bugs.freedesktop.org/show_bug.cgi?id=76077
Merge pull request #174 from crawford/teeth

networkd: Fix issues with bonding and VLANs