util/jsoncomm: add send_and_recv helper

Often, a message is being sent and followed by a call to `recv`
to wait for a reply. Create a simple helper `send_and_recv` that
does both in one method.
Add a simple check for that helper to the tests.

test/mod/test_util_jsoncomm.py

@@ -203,3 +203,16 @@ class TestUtilJsonComm(unittest.TestCase):
         a.send(ping)
         pong, _, _ = b.recv()
         self.assertEqual(ping, pong)
+
+    def test_send_and_recv(self):
+        #
+        # Test for the send and receive helper method
+
+        a, b = jsoncomm.Socket.new_pair()
+
+        ping = {"osbuild": "yes"}
+        a.send(ping)
+        pong, _, _ = b.send_and_recv(ping)
+        self.assertEqual(ping, pong)
+        pong, _, _ = a.recv()
+        self.assertEqual(ping, pong)