fix: unblock channel for cni

[camrynl]

Reason for Change:

CNI blocks when sending failure report because CNS exits and is not receiving.
Unblocking channel with select/default clause.

Issue Fixed:

Requirements:

• uses conventional commit messages
• includes documentation
• adds unit tests

Notes:

[rbtr]

I have not read through how the value sent on this channel is being used, so I don't know how messy it is. But the better pattern for this kind of binary "write once, read any" signal via a channel is to close the channel instead of sending a single item through it. Closing is non-blocking, and any reader waiting on the channel will immediately unblock and read a zero-value from the channel, and, if using two-value reads (v, ok := <-tb.cancel), a false indicating that the channel is closed.
It's important that this be the only writer for the channel, because any subsequent attempt to send on the closed channel will panic.

[tamilmani1989]

on a second thought, i think we should remove tb.Cancel() from SendReport, SendCNIMetric, SendCNIEvent from telemetry/telemetry.go. I see no value with that call and its invoked only on write failure and it doesn't close server socket since telemetrybuffer has its own copy