IQPEPHandler does not consistently identify "addressed to server" stanzas

The IQ handling in IQPEPHandler differentiates between "requests addressed to the server" and "requests addressed to a node"

It looks at the 'to' address to make the distinction: a 'null' value is interpreted as being addressed to the server. That is correct. However, a value that matches the XMPP domain exactly should also be interpreted as addressed to the server.