utils: consolidate logging to write checksum file to cache

Move log message to function that is called both by unicast and tiptorrent.

src/utils/tiptorrent.py

@@ -50,6 +50,9 @@ def tip_write_csum(image_name):
     if not os.path.exists(image_path):
         raise OgError(f'Invalid image path {image_path} for tiptorrent checksum writing')
 
+    logging.info('Calculating checksum...')
+    logging.info('*DO NOT REBOOT OR POWEROFF* the client during this time')
+
     filename = image_path + ".full.sum"
     csum = _compute_md5(image_path)
     try:
@@ -106,6 +109,4 @@ def tip_client_get(tip_addr, image_name):
     if proc.returncode != 0:
         raise OgError(f'Error fetching image {image_name} via tiptorrent')
     else:
-        logging.info('Calculating checksum...')
-        logging.info('*DO NOT REBOOT OR POWEROFF* the client during this time')
         tip_write_csum(image_name)