Description of problem:
There are some datas can't be dumped by json module, so cloud-init print an error log, and cloud-init can't write data to instance-data.json. This issue is same as bz#1631167

Version-Release number of selected component (if applicable):
RHEL7.7
cloud-init-18.2-5.el7.x86_64.rpm
cloud-init-18.5-1.el7.x86_64.rpm

How reproducible:
100%

Steps to Reproduce:
1. Create a vm on OpenStack with cloud-init installed
2. Login the vm and check cloud-init's log

Actual results:
2019-08-21 10:51:45,040 - __init__.py[WARNING]: Error persisting instance-data.json: 'utf8' codec can't decode byte 0xfa in position 0: invalid start byte

Expected results:
There shoudn't be this error log and can successfully write data to instance-data.json

Additional info:
Below is a part of code of /usr/lib/python2.7/site-packages/cloudinit/sources/__init__.py(I add some code into it to print some log)

    def get_data(self):
        """Datasources implement _get_data to setup metadata and userdata_raw.

        Minimally, the datasource should return a boolean True on success.
        """
        return_value = self._get_data()
        json_file = os.path.join(self.paths.run_dir, INSTANCE_JSON_FILE)
        if not return_value:
            return return_value

        instance_data = {
            'ds': {
                'meta-data': self.metadata,
                'user-data': self.get_userdata_raw(),
                'vendor-data': self.get_vendordata_raw()}}
        instance_data.update(
            self._get_standardized_metadata())
        try:
            LOG.error("===========")
            LOG.error(str(instance_data))
            LOG.error("===========")
            # Process content base64encoding unserializable values
            content = util.json_dumps(instance_data)
            # Strip base64: prefix and return base64-encoded-keys
            processed_data = process_base64_metadata(json.loads(content))
        except TypeError as e:
            LOG.warning('Error persisting instance-data.json: %s', str(e))
            return return_value
        except UnicodeDecodeError as e:
            LOG.warning('Error persisting instance-data.json: %s', str(e))
            return return_value
        write_json(json_file, processed_data, mode=0o600)
        return return_value

Below is the log

2019-08-21 10:51:45,039 - __init__.py[ERROR]: ===========
2019-08-21 10:51:45,040 - __init__.py[ERROR]: {'v1': {'region': None, 'local-hostname': u'yujiangcloudinitrun1', 'availability-zone': u'nova', 'instance-id': 'e75af6c7-6781-41bf-ab79-54ffb1169b75', 'cloud-name': 'openstack'}, 'ds': {'vendor-data': None, 'meta-data': {'local-hostname': u'yujiangcloudinitrun1', u'random_seed': '\xfa\xee\x1cb\x85\x8c\x1c\xf3\xb4%o\xf2n\x0b\xe5\xf4j\x86\xc5\xad;V\x1e\x82o\xb4\x93\x9f\x16\x1clRXr\xdc4\x03\xfc\xc8\xc9\xd4\x03\x01\x12?\xac\xa0.\x8b\x1f\xe1\x86\x01\x93\n"\xb1\xfe\x92\xd5t3l\xfe\xcf\xddG\x11wg\xb7f\xfb\xc2\x1f\xb3\xce\xb9\x98\xda=\xb2(\xf7\xd4\xad\x13\x93\x03]\xca6nG\xd48\xc3\x87/\xcb\x00\x9c4\xc76z\xb4\xc3\xaf=5\x99\xfb\xcbP\xbb\xb4\xa4\xc4\x82\x07ZyG\xd4\xb0Y;\xc5":\xae\x10\x9fd\xb0o\x0fNE\x06=\xe7\xb0\x80\xe7\xe4\x16-+H\x8e\xe910\x1a\x89s(\x7f\x0b\x98\x08F\x01\xb3Y\xeaA\x040Gd\xd2\xd9H\xd9\xe1yM\xc9\x93i=\xb7E\x95S\x9f\x8d\xea\xe4\t\xe4#\x12\xa9Y\xfcZ\xe9\x1e\xaf\xb3L\x0e\xd0\xedC\xb6y\xb1\x02\x8f\xd5kF\xca\xfed\xab&\xc5\x0cgCs\x17Y\xbd\xf0l.\x80"\xa6v6RL$\xb6\x8d7l\xdd\xaeE\x87\xc72\x98\xbf\xf8&\xad\xa0\'\x97\xe6\xe8\xb0\x95\xf0h,\xf9h\xd3\x91<\xb4z\xed?\x7f=W\x8e3\xdc\xbbR(\x1e\xbf\xd8\x8b\x91\xa7\xda1M\xd5Dk\x8fr\xf8\xdcM\xcbV\xf6\x8c\xa1\x00\xbe\xc5\xf1\xb1\x10\x7fU\xe9\xa5*N\xc1-\xb8\xb4\xea\x1b\x14OJ$\xd0=\xfejmL\xfeH\x1b|q\xbeh\xfb\xd0\x1a\xf7\xf9\x9b.\x1a\x95\xe8\x8b\x98\t\x9e\xe6\xd4\xd7\xd2xP\x1e\xd1"\xe8]\x89z\xcd\xd2>1(\xd4\xdb\xa3H\x1b\'@\xcfb\xdfB\xfe\xd3w\x92T\xe3\xb5\x89\xa4iqh\n)e\x9f\x0f\xc3\xfd\xf2G\x12\xf8R\x01K\',\xa5\xe79\x9d\xd9F\x92\x06\xfdA\x06]P\x98\x96\xc3\x8a\xa44\xdcO\xeakOWn\xd0\xc1\x7f\xe6,\x84ay\xf7\x10\xb4\xbcE\xcd\xab\x05\xad\xe1V\xff\x07\x83\xa2\xe5\xdb\xce\xc8R\x06\xe1I\x85\x11[:\xbd\x85[6\x1c#\xf3\xc1\xd1\xe4b\xba\xb3\x1a\xb6\xe2NzI\xee\x95\x98E|\xdc\x0e\xd1\n\x02\x99\xe0\x9e\x93\x0e\x0e\xb8\xc7Go', u'uuid': u'e75af6c7-6781-41bf-ab79-54ffb1169b75', u'availability_zone': u'nova', u'keys': [{u'type': u'ssh', u'data': u'ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQDBMeFwSPKrSdlUc2Tp9D5LTtOnyln4w6fzxyDz/TbOrwzPuFVB83kIyyeFwCh3b3Iq/5h0EFaeVFcGD3uwgtRWXlemB4zHNM3yiXaeVLwRUOS3jKtvAlYZQXNW0Kw3YirumVulo8gRXOicBMLVMDFr8uuo5qD/JxKMD8Stc+v6O7xJ9axhW/x/nqVaiG7s6gXUCDAuWpPiBGJHS5D21JRG6jWkdnDsr1hdROuKflZ7EykUiTcgQEMSwRCKqDL+MoNYGUm0VV5gHozefin49ZCYpNhpOtchcqNSLY4KpD4SNTQASzK/05wUy0GHEMLOEVF9Kgb1wOiX+0CWKyt/TVvr', u'name': u'yujiang'}], u'hostname': u'yujiangcloudinitrun1', u'launch_index': 0, u'public_keys': {u'yujiang': u'ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQDBMeFwSPKrSdlUc2Tp9D5LTtOnyln4w6fzxyDz/TbOrwzPuFVB83kIyyeFwCh3b3Iq/5h0EFaeVFcGD3uwgtRWXlemB4zHNM3yiXaeVLwRUOS3jKtvAlYZQXNW0Kw3YirumVulo8gRXOicBMLVMDFr8uuo5qD/JxKMD8Stc+v6O7xJ9axhW/x/nqVaiG7s6gXUCDAuWpPiBGJHS5D21JRG6jWkdnDsr1hdROuKflZ7EykUiTcgQEMSwRCKqDL+MoNYGUm0VV5gHozefin49ZCYpNhpOtchcqNSLY4KpD4SNTQASzK/05wUy0GHEMLOEVF9Kgb1wOiX+0CWKyt/TVvr'}, u'project_id': u'fb13525cb3a04702938869f90ebc1432', 'instance-id': u'e75af6c7-6781-41bf-ab79-54ffb1169b75', u'name': u'yujiangcloudinitrun1'}, 'user-data': ''}}
2019-08-21 10:51:45,040 - __init__.py[ERROR]: ===========

Due to the value of "random_seed" can't be handled by json, so cloud-init print the error log.