policies: fix overflow in calc_factor

Problem: issue #1129 reported `EOVERFLOW` errors for match requests for
thousands of CPUs and GPUs. Currently, `calc_factor` computes the tie
breaking factor with modular arithmetic. The computation returns
-1 when `break_tie` is divisible by `m_multiply_by`.

The negative value of `tie` causes the following integer check to
overflow, generating a spurious `EOVERFLOW` errno.

Fix the computation to ensure `tie` is strictly positive with `abs()`.

Author: milroy

resource/policies/dfu_match_multilevel_id_impl.hpp

@@ -55,7 +55,7 @@ int64_t multilevel_id_t<FOLD>::score_factor_t::calc_factor (
         return -1;
     }
     mul = add * m_multiply_by;
-    tie =  break_tie % m_multiply_by - 1;
+    tie = abs (break_tie % static_cast<int64_t> (m_multiply_by) - 1);
 
     if (mul > (std::numeric_limits<int64_t>::max () - tie)) {
         errno = EOVERFLOW;