split index hash clear from removing

On shutdown some workers sometimes still need access to index hash, so
full removing of the hash is not appropriate. However nobody forbids to
clear the hashes, and then delete them when all workers stopped

That is related and should fix #2433

Author: klirichek

src/searchd.cpp

@@ -758,12 +758,12 @@ void Shutdown () REQUIRES ( MainThread ) NO_THREAD_SAFETY_ANALYSIS
 	}
 
 	Threads::CallCoroutine ( [] {
-		SHUTINFO << "Remove local indexes list ...";
-		SafeDelete ( g_pLocalIndexes );
+		SHUTINFO << "Abandon local indexes list ...";
+		g_pLocalIndexes->ReleaseAndClear();
 
 		// unlock Distr indexes automatically done by d-tr
-		SHUTINFO << "Remove distr indexes list ...";
-		SafeDelete ( g_pDistIndexes );
+		SHUTINFO << "Abandon distr indexes list ...";
+		g_pDistIndexes->ReleaseAndClear();
 	} );
 
 	SHUTINFO << "Shutdown alone threads (if any) ...";
@@ -774,6 +774,12 @@ void Shutdown () REQUIRES ( MainThread ) NO_THREAD_SAFETY_ANALYSIS
 	if ( pPool )
 		pPool->StopAll();
 
+	SHUTINFO << "Remove local indexes list ...";
+	SafeDelete ( g_pLocalIndexes );
+
+	SHUTINFO << "Remove distr indexes list ...";
+	SafeDelete ( g_pDistIndexes );
+
 	// clear shut down of rt indexes + binlog
 	SHUTINFO << "Finish IO stats collecting ...";
 	sphDoneIOStats();