afs: Fix netns teardown to cancel the preallocation charger

In the Linux kernel, the following vulnerability has been resolved: afs: Fix netns teardown to cancel the preallocation charger Fix the teardown of an afs network namespace to make sure it cancels the work item that keeps the preallocated rxrpc call/conn/peer queue charged before incoming calls are disabled (i.e. listen 0). Also, if net->live is false because the afs netns is being deleted, make afs_charge_preallocation() skip charging and make afs_rx_new_call() avoid requeuing the charger. (This was found by AI review).