utils:fs: fix logging statement in get_filesystem_type

Call the error() logging function from the logging object instead
of the non existent log variable previously referenced.

src/utils/fs.py

@@ -228,7 +228,7 @@ def get_filesystem_type(partdev):
     cmd = shlex.split(f'blkid -o value -s TYPE {partdev}')
     proc = subprocess.run(cmd, stdout=PIPE, encoding='utf-8')
     if proc.returncode != 0:
-        log.error(f'Error getting filesystem from {partdev}')
+        logging.error(f'Error getting filesystem from {partdev}')
         return "unknown"
 
     return proc.stdout.strip()