test_time: allow exact usleep
test_time: allow exact usleep

markokr/libusual,ifduyue/libusual,rabbitt/libusual,mgjv/libusual,markokr/libusual,ifduyue/libusual,rabbitt/libusual,mgjv/libusual,rabbitt/libusual,markokr/libusual,rabbitt/libusual,ifduyue/libusual,mgjv/libusual,ifduyue/libusual,mgjv/libusual,markokr/libusual