SERVER-14802 Fixed problem with sleepmillis() on Windows due to default timer resolution on
             resolution to be set high (usually above 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.

Related to SERVER-9580

Closes #618

Signed-off-by: Benety Goh <benety@mongodb.com>