Ignore getaddr messages on Outbound connections.

Ignore getaddr messages on Outbound connections.

The only time when a client sends a "getaddr" message is when he
esatblishes an Outbound connection (see ProcessMessage() in
src/main.cpp).  Another bitcoin client is expected to receive a
"getaddr" message only on Inbound connection. Ignoring "gettaddr"
requests on Outbound connections can resolve potential privacy issues
(and as was said such request normally do not happen anyway).

Rebased-From: dca799e1db6e319fdd47e0bfdb038eab0efabb85
Github-Pull: #5442