Resovle db_host to itself for .local hosts (#19039)

* Resovle db_host to itself for .local hosts

* Add test case

* Changelog

* Changelog

* None check

Author: sethsamuel

datadog_checks_base/changelog.d/19039.fixed

@@ -0,0 +1 @@
+When resolving database hosts, always resolve a .local database host to itself

datadog_checks_base/datadog_checks/base/utils/db/utils.py

@@ -150,6 +150,9 @@ def acquire(self, key):
 
 
 def resolve_db_host(db_host):
+    if db_host and db_host.endswith('.local'):
+        return db_host
+
     agent_hostname = datadog_agent.get_hostname()
     if not db_host or db_host in {'localhost', '127.0.0.1'} or db_host.startswith('/'):
         return agent_hostname

datadog_checks_base/tests/base/utils/db/test_util.py

@@ -39,6 +39,7 @@
         ("192.0.2.1", "greater-than-or-equal-to-64-characters-causes-unicode-error-----", "192.0.2.1"),
         ("192.0.2.1", "192.0.2.1", "192.0.2.1"),
         ("192.0.2.1", "192.0.2.254", "192.0.2.1"),
+        ("postgres.svc.local", "some-pod", "postgres.svc.local"),
     ],
 )
 def test_resolve_db_host(db_host, agent_hostname, want):