imap-send.c: rearrange xcalloc arguments

xcalloc() takes two arguments: the number of elements and their size.
imap_open_store() passes the arguments in reverse order, passing the
size of an imap_store*, followed by the number to allocate.

Rearrange them so they are in the correct order.
Signed-off-by: NBrian Gesiak <modocache@gmail.com>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

imap-send.c

@@ -951,7 +951,7 @@ static struct imap_store *imap_open_store(struct imap_server_conf *srvc)
 	char *arg, *rsp;
 	int s = -1, preauth;
 
-	ctx = xcalloc(sizeof(*ctx), 1);
+	ctx = xcalloc(1, sizeof(*ctx));
 
 	ctx->imap = imap = xcalloc(sizeof(*imap), 1);
 	imap->buf.sock.fd[0] = imap->buf.sock.fd[1] = -1;