trx/ctrl_if.py: send control responses to where commands are from

When we receive a control command, we should not simply send the
response to the default destination, but send it back to the exact
IP/prt from which the command originated.

This ensures correct routing of responses even in case multiple
programs are interfacing concurrently with a control socket.

Cherry-picked from: I24a0bba6eed059b101af95dac7d059f34dd715fc
Change-Id: I1f304ea887dc957d3ad53adb1e3c56ab27d8f196
diff --git a/python/trx/udp_link.py b/python/trx/udp_link.py
index 1fae8b4..d96a6aa 100644
--- a/python/trx/udp_link.py
+++ b/python/trx/udp_link.py
@@ -45,13 +45,16 @@
 		# Check for incoming data
 		if self.sock in r_event:
 			data, addr = self.sock.recvfrom(128)
-			self.handle_rx(data.decode())
+			self.handle_rx(data.decode(), addr)
 
-	def send(self, data):
+	def send(self, data, remote = None):
 		if type(data) not in [bytearray, bytes]:
 			data = data.encode()
 
-		self.sock.sendto(data, (self.remote_addr, self.remote_port))
+		if remote is None:
+			remote = (self.remote_addr, self.remote_port)
 
-	def handle_rx(self, data):
+		self.sock.sendto(data, remote)
+
+	def handle_rx(self, data, remote):
 		raise NotImplementedError