Add docstring to pdb_signal_handler in ec2rl.py
Add docstring to pdb_signal_handler in ec2rl.py

gregbdunn/aws-ec2rescue-linux,Drudenhaus/aws-ec2rescue-linux,Drudenhaus/aws-ec2rescue-linux,gregbdunn/aws-ec2rescue-linux,Drudenhaus/aws-ec2rescue-linux,gregbdunn/aws-ec2rescue-linux