Change the mock database name to "db", because all of the codebase is using this database.

This change enables us to write unit tests without the need to patch the the database name in all of the mongo queries that look like "mongo.db.collection"

monkey/tests/unit_tests/monkey_island/cc/mongomock_fixtures.py

@@ -1,7 +1,10 @@
 import mongoengine
 import pytest
 
-MOCK_DB_NAME = "mongoenginetest"
+# Database name has to match the db used in the codebase,
+# else the name needs to be mocked during tests.
+# Currently its used like so: "mongo.db.telemetry.find()".
+MOCK_DB_NAME = "db"
 
 
 @pytest.fixture(scope="module", autouse=True)