nvme: count number of ignored interrupts

Count the number of times we're asked to process completions, but that
we ignore because the state of the qpair isn't in RECOVERY_NONE.

Sponsored by: Netflix
Reviewed by: mav, chuck
Differential Revision: https://reviews.freebsd.org/D32212

(cherry picked from commit 587aa25525e54ea775298c402acd7a647f9838fb)