man: fix a formatting on the keyctl.1 man page

Fix a formatting and a command output on
the keyctl.1 man page in a couple of places.

Signed-off-by: Vladis Dronov <vdronov@redhat.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Link: https://lore.kernel.org/r/20220510110444.14192-1-vdronov@redhat.com/