nvme: allow duplicate controller if prior controller being deleted

The current checks for whether a new controller request "matches" an
existing controller ignores controller state and checks identity strings.
There are cases where an existing controller may be in its last steps of
deletion when they are "matched" by a new connection.

Change the behavior so that the new connection ignores controllers that
are deleted.

Signed-off-by: James Smart <james.smart@broadcom.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>