libblktap: Remove trailing null byte in xs_printf

xs_printf writes the terminating null byte of the passed string to
Xenstore. When reading, the null byte is returned in the following
form which confuses tools:

sector-size = "512\000"

This patch removes the null byte from the data to write.

Signed-off-by: Kevin Wolf <kwolf@suse.de>

tools/blktap/lib/xs_api.c

@@ -132,7 +132,7 @@ int xs_printf(struct xs_handle *h, const char *dir, const char *node,
 		return ENOMEM;
 	}
 
-	ret = xs_write(h, XBT_NULL, path, buf, strlen(buf)+1);
+	ret = xs_write(h, XBT_NULL, path, buf, strlen(buf));
 	
 	free(buf);
 	free(path);