vici: Check for closed connection in Python bindings

The Python VICI library does not check if the socket is closed.
If the daemon closes the connection, _recvall() spins forever.

Closes strongswan/strongswan#56.

src/libcharon/plugins/vici/python/vici/protocol.py

@@ -33,7 +33,10 @@ class Transport(object):
         """Ensure to read count bytes from the socket"""
         data = b""
         while len(data) < count:
-            data += self.socket.recv(count - len(data))
+            buf = self.socket.recv(count - len(data))
+            if not buf:
+                raise socket.error('Connection closed')
+            data += buf
         return data