net: remove unnecessary check from AlreadyConnectedToAddress()

`CConnman::AlreadyConnectedToAddress()` searches the existent nodes by
address or by address-and-port:

```cpp
FindNode(static_cast<CNetAddr>(addr)) || FindNode(addr.ToStringAddrPort())
```

but:

* if there is a match by just the address, then the address-and-port
  search will not be evaluated and the whole condition will be `true`
* if the there is no node with the same address, then the second search
  by address-and-port will not find a match either.

The search by address-and-port is comparing against `CNode::m_addr_name`
which could be a hostname, e.g. `"node.foobar.com:8333"`, but
`addr.ToStringAddrPort()` is always going to be numeric.

src/net.cpp

@@ -367,7 +367,7 @@ CNode* CConnman::FindNode(const CService& addr)
 
 bool CConnman::AlreadyConnectedToAddress(const CAddress& addr)
 {
-    return FindNode(static_cast<CNetAddr>(addr)) || FindNode(addr.ToStringAddrPort());
+    return FindNode(static_cast<CNetAddr>(addr));
 }
 
 bool CConnman::CheckIncomingNonce(uint64_t nonce)