Allow disconnectnode() to be called with node id

disconnectnode() can currently only be called with the IP address/port
of the node the user wishes to connect. This commit allows the node to
be disconnected using the nodeid returned by getpeerinfo().

src/rpc/client.cpp

@@ -115,6 +115,7 @@ static const CRPCConvertParam vRPCConvertParams[] =
     { "bumpfee", 1, "options" },
     { "logging", 0, "include" },
     { "logging", 1, "exclude" },
+    { "disconnectnode", 1, "nodeid" },
     // Echo with conversion (For testing only)
     { "echojson", 0, "arg0" },
     { "echojson", 1, "arg1" },