timestamp of hep packets discarded in loki

[tsearle]

when hep packets arrive to the heplify server out of order to the heplify-server, the server re-writes the timestamps before sending to LOKI, causing them to appear out of order in call flow diagrams

the code doing the timestamp re-writing is located here

I propose adding a flag allow_out_of_order (similar to what vector has) to allow timestamps to be preserved.

heplify-server/remotelog/loki.go

Line 103 in c755212

// guard against entry out of order errors