site24x7_monitor_group deletion is not recognized from state

[valugi]

Steps to reproduce.

1. create a site24x7_monitor_group using TF
2. create a monitor and associate to it using TF
3. delete group and monitor using interface
4. run the same terraform

Expected behavior - group should be detected as deleted and recreated.

Actual behavior: TF will try to do an update in place and fail with an unspecified error.

Quick workaround: delete state of group.