nvme-pci: introduce RECONNECTING state to mark initializing procedure

nvme-pci: introduce RECONNECTING state to mark initializing procedure

After Sagi's commit (nvme-rdma: fix concurrent reset and reconnect),
both nvme-fc/rdma have following pattern:
RESETTING    - quiesce blk-mq queues, teardown and delete queues/
               connections, clear out outstanding IO requests...
RECONNECTING - establish new queues/connections and some other
               initializing things.
Introduce RECONNECTING to nvme-pci transport to do the same mark.
Then we get a coherent state definition among nvme pci/rdma/fc
transports.

Suggested-by: James Smart <[email protected]>
Reviewed-by: James Smart <[email protected]>
Reviewed-by: Reviewed-by: Keith Busch <[email protected]>
Signed-off-by: Jianchao Wang <[email protected]>
Signed-off-by: Christoph Hellwig <[email protected]>