Set a random seed to ensure repeatability of tests

[mattiuusitalo]

Drawback to this is that the test doesn't exercise the code as fully as more random usage would.

Pro is that we don't get false negatives from CI tests as often.

Fixes #1236

[mattiuusitalo]

Used this sort of test to see if it works with lots of repetitions. Without the change I get consistently at least one failure per 100 tries.

#!/bin/bash

for i in {0..100}
do
    if clojure -M:test:cljs-test-runner:cherry:test-cherry -c "{:optimizations :none}" -n malli.parser-test 2 >& 1 > /dev/null ; then
       echo "yes"
    else
       echo "failed! on run" $i
       exit
    fi
done