nvme: move stopping keep-alive into nvme_uninit_ctrl()

In the Linux kernel, the following vulnerability has been resolved: nvme: move stopping keep-alive into nvme_uninit_ctrl() Commit 4733b65d82bd ("nvme: start keep-alive after admin queue setup") moves starting keep-alive from nvme_start_ctrl() into nvme_init_ctrl_finish(), but don't move stopping keep-alive into nvme_uninit_ctrl(), so keep-alive work can be started and keep pending after failing to start controller, finally use-after-free is triggered if nvme host driver is unloaded. This patch fixes kernel panic when running nvme/004 in case that connection failure is triggered, by moving stopping keep-alive into nvme_uninit_ctrl(). This way is reasonable because keep-alive is now started in nvme_init_ctrl_finish().