Added __contains__ to threadlist

This patch adds the __contains__ to the APRSDThreadList
class so we can do things like

if name in APRSDThreadList:
  # do something

aprsd/threads/aprsd.py

@@ -88,6 +88,13 @@ def __new__(cls, *args, **kwargs):
             cls.threads_list = []
         return cls._instance
 
+    def __contains__(self, name):
+        """See if we have a thread in our list"""
+        for t in self.threads_list:
+            if t.name == name:
+                return True
+        return False
+
     def stats(self, serializable=False) -> dict:
         stats = {}
         for th in self.threads_list: