For operations on Bridges API if bridge-id is unknown we now return 404
instead of 400. Also a bug was fixed that caused a crash if that was a node
operation. Additionally we now also check if the given bridge is enabled when
doing the cluster operation start . Affected endpoints:
/bridges/:id/:operation,/nodes/:node/bridges/:id/:operation, where operation is one of
[start|stop|restart].
Moreover, for a node operation, EMQX checks if node name is in our cluster and
return 404 instead of 501.