Fix elasticsearch-py test_rule.py error

[nsano-rururu]

Fix
#2725

elasticsearch-py	Test Run	Send real alerts
7.0.0	〇	〇
7.10.0	✖	✖
7.10.0	〇 (fix test_rules.py )	✖
7.10.0	〇 (fix test_rules.py )	〇 (Fix initializing self.thread_data.alerts_sent for running elastalert-test-rule #2991)

[nsano-rururu]

When I run ElastAlertServer with elasticsearch-py 7.10.0, I have confirmed that the following warning appears.

16:13:49.571Z ERROR elastalert-server:
    ProcessController:  /home/node/.local/lib/python3.8/site-packages/elasticsearch/connection/base.py:190: ElasticsearchDeprecationWarning: Camel case format name dateOptionalTime is deprecated and will be removed in a future version. Use snake case name date_optional_time instead.
      warnings.warn(message, category=ElasticsearchDeprecationWarning)
    /home/node/.local/lib/python3.8/site-packages/elasticsearch/connection/base.py:190: ElasticsearchDeprecationWarning: [types removal] Using include_type_name in put mapping requests is deprecated. The parameter will be removed in the next major version.
      warnings.warn(message, category=ElasticsearchDeprecationWarning)