Bugfix: federation binds to default exchange (backport #749) #4220

Job	Run time
Compile LavinMQ	1m 2s
Format check	18s
Spec FreeBSD	3m 26s
Lint check	1m 2s
Lint javascript	13s
Lint OpenAPI	14s
Filters for fronted specs	2s
Spec	6h 0m 3s
Spec OS X	6h 0m 16s
RabbitMQ HTTP API Ruby client test	1m 8s
Bunny client test	2m 38s
RabbitMQ java client test	4m 27s
RabbitMQ HTTP API Go client test	1m 1s
Test in release mode	20s
Fronted specs	0s
	12h 16m 10s

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