Fix default send latency

[QDelta]

Do not multiply send_lat by 1000 on default path as it's already ns there.

[CLAassistant]

All committers have signed the CLA.

[Copilot]

Pull request overview

This PR fixes a bug in the send latency calculation where the default send latency value was being incorrectly multiplied by 1000. The PR description states that send_lat is already in nanoseconds on the default path and should not be multiplied.

Changes:

• Moved the multiplication by 1000 to only occur when the AS_SEND_LAT environment variable is set (converting from microseconds to nanoseconds)
• Removed the unconditional multiplication that was incorrectly applied to both the default value and environment variable values

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[Copilot]

The exception handling for std::stoi only catches std::invalid_argument but not std::out_of_range, which can also be thrown when the converted value would fall out of the range of int. Consider catching both exceptions or using a catch-all for std::exception to handle both cases consistently.

Suggested change

	exit(-1);
	exit(-1);
	} catch (const std::out_of_range& e) {
	NcclLog->writeLog(NcclLogLevel::ERROR,"send_lat set error");
	exit(-1);