Suppress ovsdb-server log messages about connections from ovs-vsctl.

Suppress ovsdb-server log messages about connections from ovs-vsctl.

In the ovsdb-server log there are fairly continuous messages like these:

Apr 26 11:27:55|15254|reconnect|INFO|unix:/tmp/stream-unix.31734.0: connected
Apr 26 11:27:55|15255|reconnect|INFO|unix:/tmp/stream-unix.31734.0: connection dropped
Apr 26 11:28:00|15256|reconnect|INFO|unix:/tmp/stream-unix.31810.0: connecting...
Apr 26 11:28:00|15257|reconnect|INFO|unix:/tmp/stream-unix.31810.0: connected
Apr 26 11:28:00|15258|reconnect|INFO|unix:/tmp/stream-unix.31810.0: connection dropped

These just indicate that ovs-vsctl is connecting to ovsdb-server from,
for example, the "vif" script.  But there's no need to log all that detail;
it's simply not useful.  This commit suppresses it.

Bug #2715.