Revert "[libc++] Add a test that uses the debug database from multiple threads"

This reverts r358591, which seems to have uncovered an actual bug and
causes the tsan CI to fail. We need to fix the bug and re-commit the
test.

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@358593 91177308-0d34-0410-b5e6-96231b3b80d8

test/libcxx/debug/containers/db_sequence_container_iterators.pass.cpp

@@ -22,9 +22,6 @@
 #include <list>
 #include <vector>
 #include <deque>
-#if !defined(_LIBCPP_HAS_NO_THREADS)
-#   include <thread>
-#endif
 #include "container_debug_tests.hpp"
 #include "debug_mode_helper.h"
 
@@ -54,7 +51,6 @@ public:
         InsertIterIterIter();
         EmplaceIterValue();
         EraseIterIter();
-        ThreadUseIter();
       }
     else {
       SpliceFirstElemAfter();
@@ -189,36 +185,6 @@ private:
     EXPECT_DEATH( CC.front() );
   }
 
-  static void ThreadUseIter() {
-#if !defined(_LIBCPP_HAS_NO_THREADS)
-    CHECKPOINT("thread iter use");
-    const size_t maxRounds = 7;
-    struct TestRunner{
-     void operator()() {
-        for (size_t count = 0; count < maxRounds; count++) {
-          const size_t containerCount = 21;
-          std::vector<Container> containers;
-          std::vector<typename Container::iterator> iterators;
-          for (size_t containerIndex = 0; containerIndex < containerCount; containerIndex++) {
-              containers.push_back(makeContainer(3));
-              Container &c = containers.back();
-              iterators.push_back(c.begin());
-              iterators.push_back(c.end());
-          }
-        }
-      }
-    };
-    TestRunner r;
-    const size_t threadCount = 13;
-    std::vector<std::thread> threads;
-    for (size_t count = 0; count < threadCount; count++)
-        threads.emplace_back(r);
-    r();
-    for (size_t count = 0; count < threadCount; count++)
-        threads[count].join();
-#endif
-  }
-
   static void EraseIterIter() {
     CHECKPOINT("testing erase iter iter invalidation");
     Container C1 = makeContainer(3);