Improve manager during updates and fix deadlock during restart before full start

[frikilax]

✨ Improve manager during updates and fix deadlock during restart before full start

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📃 Type of change

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Bug fix: non-breaking change which fixes an issue.
New feature: non-breaking change which adds functionality.

💡 Related Issue(s)

• Resolve [IDEA] Manager: update all filters when none specified #162

✒️ Description

Some improvements have been made in this PR:

Update

• when issuing a "update_filters" command with an empty "filters" or none at all, the manager will make a diff of current and newly configured filters in its conf, and start/stop filters according to this diff.
• filters updated in conf won't be taken into account, only filters deleted/added will be taken into account

Fixes

• send a response to client when command has a JSON parsing error
• remove unused restart_all() method
• remove lock on start_all()/stop_all() functions, preventing deadlock
  • those functions are called before/after other threads are active, so locking is useless
• avoid manager raising when starting a wrong filter during update

🎯 Test Environments

HBSD (12.1)

• Python (3.7.7)

Ubuntu (18.04)

• Python (3.6.9)

✔️ Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• (If other changes) I have made corresponding changes to the documentation
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes

• 🙋 I certify on my honor that all the information provided is true, and I've done all I can to deliver a high quality code