Bump libnetwork to 3ac297bc7fd0afec9051bbb47024c9bc1d75bf5b in order to
get fix 0c3d9f00 which addresses a flaw that the scalable load balancing
code revealed. Attempting to print sandbox IDs where the sandbox name
was too short results in a goroutine panic. This can occur with
sandboxes with names of 1 or 2 characters in the previous code. But due
to naming updates in the scalable load balancing code, it could now
occur for networks whose name was 3 characters and at least one of the
integration tests employed such networks (named 'foo', 'bar' and 'baz').
This update also brings in several changes as well:
* 6c7c6017 - Fix error handling about bridgeSetup
* 5ed38221 - Optimize networkDB queue
* cfa9afdb - ndots: produce error on negative numbers
* 5586e226 - improve error message for invalid ndots number
* 449672e5 - Allows to set generic knobs on the Sandbox
* 6b4c4af7 - do not ignore user-provided "ndots:0" option
* 843a0e42 - Adjust corner case for reconnect logic
Signed-off-by: Chris Telfer <ctelfer@docker.com>
