Fix BOOST random generator initialization on Windows

seed_rng::seed_rng does not produced the expected result in Windows since is using `/dev/urandom` file.

0:005> k

1. Child-SP RetAddr Call Site
   00 00000049`22dfc108 00007ff6`5193822f kernel32!CreateFileW
   ...
   0e 00000049`22dfc660 00007ff6`502228fd mesos_agent!boost::uuids::detail::seed_rng::seed_rng+0x3d [d:\repositories\mesoswin\build\3rdparty\boost-1.53.0\src\boost-1.53.0\boost\uuid\seed_rng.hpp @ 80]
   0f 00000049`22dfc690 00007ff6`502591e3 mesos_agent!boost::uuids::detail::seed<boost::random::mersenne_twister_engine<unsigned int,32,624,397,31,2567483615,11,4294967295,7,2636928640,15,4022730752,18,1812433253> >+0x4d [d:\repositories\mesoswin\build\3rdparty\boost-1.53.0\src\boost-1.53.0\boost\uuid\seed_rng.hpp @ 246]
   10 00000049`22dfc790 00007ff6`50395518 mesos_agent!boost::uuids::basic_random_generator<boost::random::mersenne_twister_engine<unsigned int,32,624,397,31,2567483615,11,4294967295,7,2636928640,15,4022730752,18,1812433253> >::basic_random_generator<boost::random::mersenne_twister_engine<unsigned int,32,624,397,31,2567483615,11,4294967295,7,2636928640,15,4022730752,18,1812433253> >+0xd3 [d:\repositories\mesoswin\build\3rdparty\boost-1.53.0\src\boost-1.53.0\boost\uuid\random_generator.hpp @ 50]
   11 00000049`22dfc800 00007ff6`500ad140 mesos_agent!id::UUID::random+0x78 [d:\repositories\mesoswin\3rdparty\stout\include\stout\uuid.hpp @ 49]
   12 00000049`22dfc870 00007ff6`5007ff55 mesos_agent!mesos::internal::slave::Framework::launchExecutor+0x70 [d:\repositories\mesoswin\src\slave\slave.cpp @ 6301]
   13 00000049`22dfd520 00007ff6`502a0a35 mesos_agent!mesos::internal::slave::Slave::_run+0x2455 [d:\repositories\mesoswin\src\slave\slave.cpp @ 1990]
   ...
   0:005> du @rcx
   000001d7`cc55fb60 "/dev/urandom"