s3-cloudconfig-bootstrap.sh accountId bug

[Xueshan Feng]

The script uses curl -s http://169.254.169.254/latest/dynamic/instance-identity/document | grep -Eo '([[:digit:]]{12})' to generate AWS accountId, but in rare cases when an instance id contains consecutive 12 digits, the accountId generated would have two numbers which is complete bogus, causing the bootstrap to fail.