nvmf/ctrlr: remove assert for qpair state.

Historically, we have immediately called the qpair
fini function directly from _spdk_nvmf_qpair_destroy.

However, to fix a race with initiators where we can get
a duplicate QID from the initiator, we will have to clear
the QID bit before calling qpair_fini. Clearing the QID bit
must be done on the controller thread, so we have to pass at
least two messages between calling _spdk_nvmf_qpair_destroy
and qpair_fini. This leaves a gap where we can poll the poll group
and reap completions for the qpair before we call qpair_fini and drain
all of the requests related with the qpair.

Signed-off-by: Seth Howell <seth.howell@intel.com>
Change-Id: I337a0608f88fdda132b8a629a508c0263d2261c5
Reviewed-on: https://review.spdk.io/gerrit/c/spdk/spdk/+/1881


Community-CI: Mellanox Build Bot
Community-CI: Broadcom CI
Tested-by: SPDK CI Jenkins <sys_sgci@intel.com>
Reviewed-by: Aleksey Marchuk <alexeymar@mellanox.com>
Reviewed-by: Ben Walker <benjamin.walker@intel.com>
Reviewed-by: Shuhei Matsumoto <shuhei.matsumoto.xt@hitachi.com>