nvme-fabrics: introduce init command check for a queue that is not alive

When the fabrics queue is not alive and fully functional, no commands
should be allowed to pass but connect (which moves the queue to a fully
functional state). Any other command should be failed, with either
temporary status BLK_STS_RESOUCE or permanent status BLK_STS_IOERR.

This is shared across all fabrics, hence move the check to fabrics
library.

Signed-off-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Christoph Hellwig <hch@lst.de>