Seed Lua's number generator on nginx worker init

[quinox]

During testing I discovered Lua doesn't seed itself, resulting in the same request IDs showing in my logs. I've implemented seeding for Unix-like systems using /dev/urandom; Lots of pages on the internet suggest os.time() but this seems like it would make different nginx workers seed with the same number which is undesirable (but I'm no expert, so I could be wrong).

--restarted nginx (no seed)
::1 - - [15/Aug/2017:15:05:26 +0200] "GET / HTTP/1.1" request_id=KSG6-N7L5TK0U-1TMT69XB
::1 - - [15/Aug/2017:15:05:26 +0200] "GET / HTTP/1.1" request_id=U01R-EYZDA9VY-LR2DNYQ3
::1 - - [15/Aug/2017:15:05:26 +0200] "GET / HTTP/1.1" request_id=2OJS-2IPJ3N27-TOZOTZDD
--restarted nginx (no seed)
::1 - - [15/Aug/2017:15:05:33 +0200] "GET / HTTP/1.1" request_id=KSG6-N7L5TK0U-1TMT69XB
::1 - - [15/Aug/2017:15:05:33 +0200] "GET / HTTP/1.1" request_id=U01R-EYZDA9VY-LR2DNYQ3
::1 - - [15/Aug/2017:15:05:33 +0200] "GET / HTTP/1.1" request_id=2OJS-2IPJ3N27-TOZOTZDD
--restarted nginx (seeded)
::1 - - [15/Aug/2017:15:05:45 +0200] "GET / HTTP/1.1" request_id=EQKT-I0AA72YT-S5A9GSN9
::1 - - [15/Aug/2017:15:05:45 +0200] "GET / HTTP/1.1" request_id=EIXC-X5J1ANTW-KJXZS8BE
::1 - - [15/Aug/2017:15:05:45 +0200] "GET / HTTP/1.1" request_id=TWNB-360U791Q-DNNEOK1O
--restarted nginx (seeded)
::1 - - [15/Aug/2017:15:05:55 +0200] "GET / HTTP/1.1" request_id=SF8O-V264GYXS-24408CF5
::1 - - [15/Aug/2017:15:05:55 +0200] "GET / HTTP/1.1" request_id=DRUE-C66R00Q3-7XSW5YZP
::1 - - [15/Aug/2017:15:05:55 +0200] "GET / HTTP/1.1" request_id=89KS-FZR9M8RB-5R0I1S3A