Display error if server is not connected to analytics

[rozetko]

Steps to reproduce:

• run hastic/server without hastic/analytics
• create analytic unit
• click Apply

Expected behavior:

• "server is not connected to analytics" error

Actual behavior:

• not-ending "Learning" analytic unit status

[jonyrock]

I only worries if we show all these warnings and errors in a consitent way