fixed inconsistent driver send() declaration.

The KISS drivers aren't adhering to the protocol for
defining the send() method.  both now specify that they
return a bool.

aprsd/client/drivers/serialkiss.py

@@ -192,12 +192,15 @@ class SerialKISSDriver(KISSDriver):
                 self._connected = False
                 break
 
-    def send(self, packet: core.Packet):
+    def send(self, packet: core.Packet) -> bool:
         """Send an APRS packet.
 
         Args:
             packet: APRS packet to send (Packet or Message object)
 
+        Returns:
+            bool: True if packet was sent successfully
+
         Raises:
             Exception: If not connected or send fails
         """

aprsd/client/drivers/tcpkiss.py

@@ -96,12 +96,15 @@ class TCPKISSDriver(KISSDriver):
         else:
             LOG.warning('close: socket not initialized. no reason to close.')
 
-    def send(self, packet: core.Packet):
+    def send(self, packet: core.Packet) -> bool:
         """Send an APRS packet.
 
         Args:
             packet: APRS packet to send (Packet or Message object)
 
+        Returns:
+            bool: True if packet was sent successfully
+
         Raises:
             Exception: If not connected or send fails
         """