OVS agent: Correct bridge setup ordering

This patch fixes three issues that combined to break tunnel networks.

The first issue was the the failure mode was being set on the
integration bridge after the canary flow was installed. This
immediately wiped out the canary flow.

The second problem was that the main loop would sync tunnel networks
right before resetting the tunnel bridge when the canary flow was
missing. This meant that it would sync all of the tunnels via RPC and
then wipe them out.

The final issue was that after resetting the tunnel bridge in the
main loop, the tunnel_sync variable was not set to True, so the
tunnels would never be resynchronized.

This patch addresses the three issues in the following ways:
1. Set the failure mode on the bridge before the canary flow is
installed.
2. Run the OVS restart logic before the tunnel synchronization.
3. If the restart logic is triggered, set tunnel_sync to True to
trigger synchronization.

Closes-Bug: #1292105
Change-Id: I6381e3fee49910127c420dd2e3205c64cdb9e185