First request always mapps as +inf bucket instead of real bucket

[Veres72]

The first request always maps as +inf bucket instead of real bucket, while all the following is correct.

The first request

nginx_vts_server_request_duration_seconds_bucket{host="_",le="0.001"} 0
nginx_vts_server_request_duration_seconds_bucket{host="_",le="1.000"} 0
nginx_vts_server_request_duration_seconds_bucket{host="_",le="100000.000"} 0
nginx_vts_server_request_duration_seconds_bucket{host="_",le="+Inf"} 1
nginx_vts_server_request_duration_seconds_sum{host="_"} 0.000
nginx_vts_server_request_duration_seconds_count{host="_"} 1

After several requests

nginx_vts_server_request_duration_seconds_bucket{host="_",le="0.001"} 11
nginx_vts_server_request_duration_seconds_bucket{host="_",le="1.000"} 11
nginx_vts_server_request_duration_seconds_bucket{host="_",le="100000.000"} 11
nginx_vts_server_request_duration_seconds_bucket{host="_",le="+Inf"} 12
nginx_vts_server_request_duration_seconds_sum{host="_"} 0.000
nginx_vts_server_request_duration_seconds_count{host="_"} 12