collector: send snmptrap on no-signal

[netoptimizer]

When no-signal is detected for a given stream, an snmptrap should be generated.

[netoptimizer]

Considerations:

Want to have both a trap:

• when the signal stops
• and a trap when/if it starts again

[netoptimizer]

Questions:

• What OID should I use?
• What should the trap contain (at least: multicast dst, and src IP)