fs: switch order of CAP_DAC_OVERRIDE and CAP_DAC_READ_SEARCH checks

generic_permission() presently checks CAP_DAC_OVERRIDE prior to
CAP_DAC_READ_SEARCH.  This can cause misleading audit messages when
using a LSM such as SELinux or AppArmor, since CAP_DAC_OVERRIDE
may not be required for the operation.  Flip the order of the
tests so that CAP_DAC_OVERRIDE is only checked when required for
the operation.

Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>
Acked-by: John Johansen <john.johansen@canonical.com>
Reviewed-by: Serge Hallyn <serge@hallyn.com>
Acked-by: James Morris <james.l.morris@oracle.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>