Bug 1738607

Description of problem:
There is a new error in fixing bug 1467391. The file is malformed and is failed to load in the latest "RHEL-7.7_HVM_GA-20190716-x86_64-0-Hourly2-GP2" AMI.

The following is the error log:
2019-08-07 14:33:27,259 - handlers.py[DEBUG]: finish: init-local/search-Ec2Local: SUCCESS: found local data from DataSourceEc2Local
2019-08-07 14:33:27,259 - stages.py[INFO]: Loaded datasource DataSourceEc2Local - DataSourceEc2Local
2019-08-07 14:33:27,260 - util.py[DEBUG]: Reading from /etc/cloud/cloud.cfg (quiet=False)
2019-08-07 14:33:27,260 - util.py[DEBUG]: Read 1236 bytes from /etc/cloud/cloud.cfg
2019-08-07 14:33:27,260 - util.py[DEBUG]: Attempting to load yaml from string of length 1236 with allowed root types (<type 'dict'>,)
2019-08-07 14:33:27,269 - util.py[DEBUG]: Reading from /etc/cloud/cloud.cfg.d/99-datasource.cfg (quiet=False)
2019-08-07 14:33:27,269 - util.py[DEBUG]: Read 59 bytes from /etc/cloud/cloud.cfg.d/99-datasource.cfg
2019-08-07 14:33:27,269 - util.py[DEBUG]: Attempting to load yaml from string of length 59 with allowed root types (<type 'dict'>,)
2019-08-07 14:33:27,270 - util.py[WARNING]: Failed loading yaml blob. Invalid format at line 1 column 1: "while parsing a block mapping
  in "<string>", line 1, column 1:
    'datasource_list': [
    ^
expected <block end>, but found ','
  in "<string>", line 4, column 6:
        ],
         ^"
2019-08-07 14:33:27,270 - util.py[DEBUG]: Reading from /etc/cloud/cloud.cfg.d/05_logging.cfg (quiet=False)
2019-08-07 14:33:27,270 - util.py[DEBUG]: Read 1821 bytes from /etc/cloud/cloud.cfg.d/05_logging.cfg
2019-08-07 14:33:27,270 - util.py[DEBUG]: Attempting to load yaml from string of length 1821 with allowed root types (<type 'dict'>,)
2019-08-07 14:33:27,277 - util.py[DEBUG]: Reading from /run/cloud-init/cloud.cfg (quiet=False)
2019-08-07 14:33:27,277 - util.py[DEBUG]: Attempting to load yaml from string of length 0 with allowed root types (<type 'dict'>,)
2019-08-07 14:33:27,278 - util.py[DEBUG]: loaded blob returned None, returning default.
2019-08-07 14:33:27,279 - util.py[DEBUG]: Attempting to remove /var/lib/cloud/instance
2019-08-07 14:33:27,280 - util.py[DEBUG]: Creating symbolic link from '/var/lib/cloud/instance

[root@ip-10-22-2-4 log]# rpm -qa|grep cloud-init
cloud-init-18.5-3.el7.x86_64

Version-Release number of selected component (if applicable):
kernel-3.10.0-1062.el7.x86_64

How reproducible:

Steps to Reproduce:
1. start a instance using RHEL7.7 GA AMI.
2. check "/var/log/cloud-init.log"

Actual results:
99-datasource.cfg is failed to load

Expected results:
No such error.

Additional info:
- N/A