User impact:
User is not able to see alerts if both Integrated Alerting and STT are enabled

Steps to reproduce:

• Set up PMM with an interval for STT checks execution
  -e PERCONA_TEST_CHECKS_INTERVAL=10s

• Navigate to PMM>>>Settings and enable STT and Integrated alerting and Apply Settings.

• Add slack or email settings to Communication settings to be able to receive notifications.

• Navigate to the Integrating Alerts menu

• Create a Notification channel

• Add rule e.g. "MySQL down" and specify rule details

• Emulate mysql instance down and verify Alerts tab

Actual result:
Error is shown 'Rule with ID "mysql_version" not found'
Expected result:
No errors and Alert is shown in Alerts list

Workaround:
Not to enable STT in Settings.