net: only disconnect if fDisconnect has been set
net: only disconnect if fDisconnect has been set

These conditions are problematic to check without locking, and we shouldn't be
relying on the refcount to disconnect.

dagurval/bitcoinxt,bitcoinxt/bitcoinxt,dagurval/bitcoinxt,bitcoinxt/bitcoinxt,dagurval/bitcoinxt,bitcoinxt/bitcoinxt,dagurval/bitcoinxt,bitcoinxt/bitcoinxt,dagurval/bitcoinxt,bitcoinxt/bitcoinxt,dagurval/bitcoinxt,bitcoinxt/bitcoinxt