func (c *FakeClient) IsExist(instanceID string) (bool, error) {
	c.IsExistCalled = true
	return c.Exist, c.IsExistErr
}
func (c *FakeClient) IsExist(instanceID string) (bool, error) {
	c.IsExistCalled = true
	return c.Exist, c.IsExistErr
}
// IsExist indicates whether the agent settings for a given instance ID exists w/i empty.