nvme-core: add missing fault-injection cleanup

Add missing fault-injection cleanup in nvme_init_ctrl() in the error
unwind path that also fixes following message for blktests:-

linux-block (for-next) # grep debugfs debugfs-err.log
[  147.853464] debugfs: Directory 'nvme1' with parent '/' already present!
[  147.853973] nvme1: failed to create debugfs attr
[  148.802490] debugfs: Directory 'nvme1' with parent '/' already present!
[  148.803244] nvme1: failed to create debugfs attr
[  148.877304] debugfs: Directory 'nvme1' with parent '/' already present!
[  148.877775] nvme1: failed to create debugfs attr
[  149.816652] debugfs: Directory 'nvme1' with parent '/' already present!
[  149.818011] nvme1: failed to create debugfs attr

Signed-off-by: Chaitanya Kulkarni <kch@nvidia.com>
Tested-by: Yi Zhang <yi.zhang@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Keith Busch <kbusch@kernel.org>