[debug] improve run_check compatibility

Datadog Agent checks do not necessarily inherit directly from the
`AgentCheck` class. When it is the case, the `run_check` DEBUG method
would fail loading the check.
This happens with WMI checks for instance.

Allow the `run_check` DEBUG method to load any agent check that inherits
from the `AgentCheck`.

Author: Yann MAHE

utils/debug.py

@@ -52,7 +52,7 @@ def get_check(name, config_str):
     check_class = None
     classes = inspect.getmembers(check_module, inspect.isclass)
     for name, clsmember in classes:
-        if AgentCheck in clsmember.__bases__:
+        if issubclass(clsmember, AgentCheck) and clsmember != AgentCheck:
             check_class = clsmember
             break
     if check_class is None: