SERVER-9580 Fixed problem with sleepmillis() on Windows due to default timer resolution being typically higher than 15ms

All sleepmillis() calls with values lesser than timer resolution will sleep AT LEAST the timer resolution value, making Mongo be really slow on certain use cases. Like when implementing consumer/producer patterns using capped collections to stream objects back and forth
We should just set it once per process in [platform_init.cpp](https://github.com/mongodb/mongo/blob/master/src/mongo/util/platform_init.cpp). We never actually
need to call timeEndPeriod as part of shutdown since Windows will automatically
unset the time period when the process terminates.