RAFT Fix arbitrary code execution vulnerability in checkpoint feature (…

…ShishirPatil#415)

Replaced `eval()` by `int()` when loading the checkpoint file to remove
the possibility of executing arbitrary code.

Co-authored-by: Shishir Patil <[email protected]>

raft/raft.py

@@ -285,7 +285,7 @@ def save_checkpoint(state, filename):
 
 def load_checkpoint(filename):
     with open(filename, 'r') as f:
-        return eval(f.read())
+        return int(f.read())
 
 def main():
     global ds