Replace exit() with abort() in case of NuRaft errors

CI founds [1]:

    WARNING: ThreadSanitizer: data race (pid=99)
      Write of size 8 at 0x7b14002192b0 by thread T27:
        12 std::__1::map<>
        13 DB::OpenedFileCache::~OpenedFileCache() obj-x86_64-linux-gnu/../src/IO/OpenedFileCache.h:27:7 (clickhouse+0xac66de6)
        14 cxa_at_exit_wrapper(void*) crtstuff.c (clickhouse+0xaa3646f)
        15 decltype(*(std::__1::forward<nuraft::raft_server*&>(fp0)).*fp()) std::__1::__invoke<void ()(), nuraft::raft_server*&, void>()

      Previous read of size 8 at 0x7b14002192b0 by thread T37 (mutexes: write M732116415018761216):
        4 DB::OpenedFileCache::get() obj-x86_64-linux-gnu/../src/IO/OpenedFileCache.h:47:37 (clickhouse+0xac66784)

    Thread T27 'nuraft_commit' (tid=193, running) created by main thread at:
    ...
    Thread T37 'MergeMutate' (tid=204, running) created by main thread at:
    ...

But it also reports that the mutex was already destroyed:

    Mutex M732116415018761216 is already destroyed.

The problem is that [nuraft can call `exit()`](1707a7572a/src/handle_commit.cxx (L157-L158)) which will call atexit handlers:

    2022.02.17 22:54:03.495450 [ 193 ] {} <Error> RaftInstance: background committing thread encounter err Memory limit (total) exceeded: would use 56.56 GiB (attempt to allocate chunk of 8192 bytes), maximum: 55.82 GiB, exiting to protect the system

  [1]: https://s3.amazonaws.com/clickhouse-test-reports/33057/5a8cf3ac98808dadf125068a33ed9c622998a484/fuzzer_astfuzzertsan,actions//report.html

Let's replace exit() with abort() to avoid this.

Signed-off-by: Azat Khuzhin <a.khuzhin@semrush.com>

src/Coordination/KeeperStateManager.cpp

@@ -115,6 +115,15 @@ void KeeperStateManager::loadLogStore(uint64_t last_commited_index, uint64_t log
     log_store->init(last_commited_index, logs_to_keep);
 }
 
+void KeeperStateManager::system_exit(const int /* exit_code */)
+{
+    /// NuRaft itself calls exit() which will call atexit handlers
+    /// and this may lead to an issues in multi-threaded program.
+    ///
+    /// Override this with abort().
+    abort();
+}
+
 ClusterConfigPtr KeeperStateManager::getLatestConfigFromLogStore() const
 {
     auto entry_with_change = log_store->getLatestConfigChange();

src/Coordination/KeeperStateManager.h

@@ -73,7 +73,7 @@ public:
 
     nuraft::ptr<nuraft::srv_config> get_srv_config() const { return configuration_wrapper.config; }
 
-    void system_exit(const int /* exit_code */) override {}
+    void system_exit(const int exit_code) override;
 
     int getPort() const
     {