Remove old hack thread_local for macosx

Change-Id: I6d19a6b933d9e38a5e310e2d4dd0f1a97312bc3e
Reviewed-on: https://review.couchbase.org/c/kv_engine/+/189928
Tested-by: Build Bot <[email protected]>
Reviewed-by: Paolo Cocchi <[email protected]>

Author: trondn

engines/ep/src/probabilistic_counter.cc

@@ -18,27 +18,10 @@ static std::uniform_real_distribution<> dis{0.0, 1.0};
 
 // Generate and return a random double value
 double ProbabilisticCounterImpl::generateRandom() {
-/*
- * Use a thread_local random number generator.  Based on the
- * following: https://stackoverflow.com/a/21238187
- */
-#if __APPLE__
     /*
-     * Due to Apple's clang disabling the thread_local keyword
-     * support we have to have the code below.
-     * @todo Fixed in XCode 8 (MacOS 10.11.5 / 10.12 or later).
+     * Use a thread_local random number generator.  Based on the
+     * following: https://stackoverflow.com/a/21238187
      */
-    static __thread bool seeded = false;
-    static __thread std::minstd_rand::result_type generatorState = 0;
-    if (!seeded) {
-        seeded = true;
-        generatorState = std::random_device()();
-    }
-    std::minstd_rand gen(generatorState);
-    // Move the generator state forward
-    generatorState = gen();
-#else
     static thread_local std::minstd_rand gen{std::random_device()()};
-#endif
     return dis(gen);
 }