Delay FreePBX restart on update if there are active calls

[Stell0]

When Nethvoice is updated, freepbx container is restarted even if there are active calls.
Check if there are active calls and avoid restarting it if there are.
After a timeut, restart it anyway.

[Stell0]

Test case:

• update nethvoice
• check that freepbx container is restarted only if there aren't active calls (or after a 24h timeout)