Various methods in counters.cpp are prone to races, so it makes sense to add them to valgrind.suppressions.

These OpCounters methods use the RARELY macro, which relies on a static counter that multiple threads can modify:

OpCounters::gotCommand()
OpCounters::gotDelete()
OpCounters::gotGetMore()
OpCounters::gotInsert()
OpCounters::gotQuery()
OpCounters::gotUpdate()

And NetworkCounter::hit has this comment:

// don't care about the race as its just a counter