Take away the ability for sys_capset() to affect processes other than current.

This means that current will not need to lock its own credentials when reading
them against interference by other processes.

This has effectively been the case for a while anyway, since:

 (1) Without LSM enabled, sys_capset() is disallowed.

 (2) With file-based capabilities, sys_capset() is neutered.
Signed-off-by: NDavid Howells <dhowells@redhat.com>
Acked-by: NSerge Hallyn <serue@us.ibm.com>
Acked-by: NAndrew G. Morgan <morgan@kernel.org>
Acked-by: NJames Morris <jmorris@namei.org>
Signed-off-by: NJames Morris <jmorris@namei.org>