nvmet-fcloop: access fcpreq only when holding reqlock

[ Upstream commit 47a827cd ]

The abort handling logic expects that the state and the fcpreq are only
accessed when holding the reqlock lock.

While at it, only handle the aborts in the abort handler.

Signed-off-by: Daniel Wagner <wagi@kernel.org>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>