Use watchdog instead of watchfiles to monitor for new images on the file system

tests/conftest.py

@@ -400,10 +400,12 @@ def run_around_tests(monkeypatch, config, port_manager):
     config.settings.VMware.vmrun_path = tmppath
     config.settings.Dynamips.dynamips_path = tmppath
 
-
     # Force turn off KVM because it's not available on CI
     config.settings.Qemu.enable_hardware_acceleration = False
 
+    # avoid monitoring for new images while testing
+    config.settings.Server.auto_discover_images = False
+
     monkeypatch.setattr("gns3server.utils.path.get_default_project_directory", lambda *args: os.path.join(tmppath, 'projects'))
 
     # Force sys.platform to the original value. Because it seems not be restored correctly after each test