Do not make daemon output zero byte

This byte is useless and can be seen in zsh output (strange that it did not 
cause bugs so far, at least none I know about). It may have been needed if any 
client was supposed to hold connection with daemon for a few runs, but all 
current clients work in “request → output response → exit” fashion without 
caring about terminating newline and definitely without preserving connection to 
daemon accross runs.

scripts/powerline-daemon

@@ -137,7 +137,7 @@ def do_read(conn, timeout=2.0):
 
 def do_write(conn, result):
 	try:
-		eintr_retry_call(conn.sendall, result + b'\0')
+		eintr_retry_call(conn.sendall, result)
 	except Exception:
 		pass