sctp: do not enable peer features if we can't do them.

Do not enable peer features like addip and auth, if they
are administratively disabled localy.  If the peer resports
that he supports something that we don't, neither end can
use it so enabling it is pointless.  This solves a problem
when talking to a peer that has auth and addip enabled while
we do not.  Found by Andrei Pelinescu-Onciul <andrei@iptel.org>.

Signed-off-by: Vlad Yasevich <vladislav.yasevich@hp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>