vswitch: reduce passes through config loop

vswitch: reduce passes through config loop

When vswitchd configures itself, it loops through the bridges to pull
relevant configuration information from vswitchd.conf.  Configuration
for determining the dpid, controller, and NetFlow was inside a loop for
configuring a bridge's interfaces.  This meant that these configuration
parameters were being re-set for each interface in the bridge as opposed
to just once for the bridge.  This change pushes this configuration
outside of that interface loop.  The LIST_FOR_EACH_SAFE macro to loop
through the bridges is switched to LIST_FOR_EACH, since bridges are not
deleted in this loop.