nvme/064: add test for authentication with dhchap keys

[hreinecke]

With the latest patchset the authentication code will store the authentication secrets in the kernel keyring, so add a testcase using pre-populated keys for authentication.

[kawasaki]

@hreinecke When I run the test case on the kernel on nvme-6.16 branch git hash bf4d87cba2d7 with the
series titled "[PATCHv2 0/9] nvme-auth: switch to use the kernel keyring"", I observe the failure below.

The keyctl revoke command fails with the Permission denied error. If you can think of cause of this error, please share.

nvme/064 (tr=tcp) (Test re-authentication with dhchap keys)  [failed]
    runtime  2.851s  ...  3.667s
    --- tests/nvme/064.out      2025-06-02 21:50:31.999324200 +0900
    +++ /home/shin/Blktests/blktests/results/nodev_tr_tcp/nvme/064.out.bad      2025-06-03 20:20:59.766542767 +0900
    @@ -2,12 +2,16 @@
     Re-authenticate with original host key
     Renew host key on the controller
     Re-authenticate with new host key
    +keyctl_revoke: Permission denied
     Renew ctrl key on the controller
     Re-authenticate with new ctrl key
    +keyctl_revoke: Permission denied
    ...
    (Run 'diff -u tests/nvme/064.out /home/shin/Blktests/blktests/results/nodev_tr_tcp/nvme/064.out.bad' to see the entire diff)

I tried to create a key and revoke it as below. It looks like that the write permission is not added to the key, then the revoke fails.

$ sudo keyctl add dhchap 4285b31e-bf45-441c-98b6-abfe0295d364 DHHC-1:01:G+ERaogIFmZHEvwlRSFzmHY2DU1Z05aa3R6F3jIhrXF+95Bz: %:.nvme
259544714
$ sudo keyctl revoke "%dhchap:4285b31e-bf45-441c-98b6-abfe0295d364"
keyctl_revoke: Permission denied
$ sudo keyctl show %:.nvme
Keyring
1050098691 ---lswrv      0     0  keyring: .nvme
 259544714 --als-rv      0     0   \_ dhchap: 4285b31e-bf45-441c-98b6-abfe0295d364