Remove duplicate network state checks before shutdown network

[sureshanaparti]

Description

This PR removes duplicate network state checks before shutdown network (seems these checks again are not required, maybe added while resolving conflicts),and adds unit tests for the network state checks in shutdown network.

Keeping this checks after acquiring lock, removed others. https://github.com/apache/cloudstack/blob/3f9dd4dc07ff40a4e0216014715e4fe37fc46d28/engine/orchestration/src/main/java/org/apache/cloudstack/engine/orchestration/NetworkOrchestrator.java#L3042-L3049

Types of changes

• [ ] Breaking change (fix or feature that would cause existing functionality to change)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Bug fix (non-breaking change which fixes an issue)
• [ ] Enhancement (improves an existing feature and functionality)
• [x] Cleanup (Code refactoring and cleanup, that may add test cases)
• [ ] build/CI

Feature/Enhancement Scale or Bug Severity

Feature/Enhancement Scale

• [ ] Major
• [ ] Minor

Bug Severity

• [ ] BLOCKER
• [ ] Critical
• [ ] Major
• [ ] Minor
• [ ] Trivial

Screenshots (if appropriate):

How Has This Been Tested?

How did you try to break this feature and the system with this change?