Refs #RHIROS-1176 - handle condition where description is unavailable

[upadhyeammit]

Why do we need this change? 💭

1. It may happen that description is not available for instance_type, hence in that condition we would return null description but api call should succeed
2. The cache is not working for the method, if I update the file then its not reflecting the change. I tried with multiple combinations and hence caching has been removed for instance_types_desc_dict()

Documentation update? 📝

• Yes
• No

Security Checklist 🔒

Upon raising this PR please go through RedHatInsights/secure-coding-checklist

💂‍♂️ Checklist 🎯

• Bugfix
• New Feature
• Refactor
• Unittests Added
• DRY code
• Dependency Added
• DB Migration Added

Additional 📣

Feel free to add any other relevant details such as links, notes, screenshots, here.

[codecov-commenter]

Codecov Report

Attention: 12 lines in your changes are missing coverage. Please review.

Files	Coverage Δ
ros/api/common/instance_types_helper.py	100.00% <100.00%> (ø)
ros/api/routes.py	100.00% <100.00%> (ø)
ros/api/v1/hosts.py	86.58% <100.00%> (+0.38%)	⬆️
ros/lib/models.py	100.00% <100.00%> (ø)
ros/processor/insights_engine_consumer.py	72.17% <100.00%> (+1.53%)	⬆️
ros/api/common/utils.py	91.30% <77.77%> (-2.03%)	⬇️
ros/lib/utils.py	86.05% <76.47%> (-1.13%)	⬇️
ros/api/v1/suggested_instance_types.py	88.88% <88.88%> (ø)

📢 Thoughts on this report? Let us know!.

[upadhyeammit]

closing this one as the changes are grouped in another pr: #383