Check _isWindows() when initializing MongoRunner.EXIT_ABORT

std::abort() on Windows returns a different exit code than other platforms, and so when we expect a process to be aborted, we first consult _isWindows before passing in the expected exit code (Either MongoRunner.EXIT_ABORT or MongoRunner.EXIT_ABRUPT). Here is an example of this in the test oplog_replay_on_startup_with_bad_op.js. 

Instead, we should check _isWindows when MongoRunner.EXIT_ABORT is initialized in servers.js similarly to how MongoRunner.SIGKILL is initialized here.