nvme-fabrics: unify common code in admin and io queue connect

To simplify code maintenance, it is recommended to avoid duplicating
code.

Tested-by: Noam Gottlieb <ngottlieb@nvidia.com>
Reviewed-by: Israel Rukshin <israelr@nvidia.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Max Gurtovoy <mgurtovoy@nvidia.com>
Signed-off-by: Keith Busch <kbusch@kernel.org>