nvmet-tcp: fix kernel crash if commands allocation fails

In the Linux kernel, the following vulnerability has been resolved: nvmet-tcp: fix kernel crash if commands allocation fails If the commands allocation fails in nvmet_tcp_alloc_cmds() the kernel crashes in nvmet_tcp_release_queue_work() because of a NULL pointer dereference. nvmet: failed to install queue 0 cntlid 1 ret 6 Unable to handle kernel NULL pointer dereference at virtual address 0000000000000008 Fix the bug by setting queue->nr_cmds to zero in case nvmet_tcp_alloc_cmd() fails.