cov-test-determinism: use the same RNG seed as in travis.yml

We added this facility so that we could get deterministic PRNG
behavior for coverage testing on tests that use a replaced PRNG.
We need to have our coverage determinism tool test for this as well.

scripts/test/cov-test-determinism.sh

@@ -25,6 +25,9 @@ else
 fi
 
 if test "$run" = 1; then
+    # same seed as in travis.yml
+    TOR_TEST_RNG_SEED="636f766572616765"
+    export TOR_TEST_RNG_SEED
     while true; do
         make reset-gcov
         CD=coverage-raw/coverage-$(date +%s)