Write a point with precision in microseconds not work correctly

[thinkUpRoger]

testing version 3.1.1
with example basic write

if precision is configurare in micro seconds the point is write in 1970 date

#define WRITE_PRECISION WritePrecision::US client.setWriteOptions(WRITE_PRECISION,100,200,180,true);

this write a point in 1970

Fix in InfluxDBClient.cpp file

Write correctly date