Add e2e test case for maintenance mode interaction

[johscheuer]

Description

This PR adds two tests cases for testing the interaction with the maintenance mode. In the future we can extend those test cases.

Type of change

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• Other

Discussion

Testing

Ran manually:

Ran 2 of 2 Specs in 930.483 seconds
SUCCESS! -- 2 Passed | 0 Failed | 0 Pending | 0 Skipped
--- PASS: TestOperatorHA (930.49s)
PASS
ok      github.com/FoundationDB/fdb-kubernetes-operator/e2e/test_operator_maintenance_mode      930.898s

Documentation

Follow-up

[foundationdb-ci]

Result of fdb-kubernetes-operator-pr on Linux CentOS 7

• Commit ID: eb6b820
• Duration 1:45:14
• Result: ❌ FAILED
• Error: Error while executing command: if $fail_test; then exit 1; fi. Reason: exit status 1
• Build Log terminal output (available for 30 days)
• Build Workspace zip file of the working directory (available for 30 days)

[foundationdb-ci]

Result of fdb-kubernetes-operator-pr on Linux CentOS 7

• Commit ID: ebfba0a
• Duration 1:42:25
• Result: ✅ SUCCEEDED
• Error: N/A
• Build Log terminal output (available for 30 days)
• Build Workspace zip file of the working directory (available for 30 days)