Add an advanced setting to kill sessions on logout to try to prevent issue 4147

sources/iTermAdvancedSettingsModel.h

@@ -183,5 +183,6 @@
 + (double)underlineCursorOffset;
 + (BOOL)logRestorableStateSize;
 + (NSString *)autoLogFormat;
++ (BOOL)killSessionsOnLogout;
 @end

sources/iTermAdvancedSettingsModel.m

@@ -273,5 +273,6 @@ DEFINE_BOOL(trackingRunloopForLiveResize, YES, @"Experimental Features: Use a tr
 DEFINE_BOOL(enableAPIServer, NO, @"Experimental Features: Enable websocket API server.\nYou must restart iTerm2 for this change to take effect.");
 DEFINE_BOOL(useGCDUpdateTimer, YES, @"Experimental Features: Use GCD-based update timer instead of NSTimer.\nThis should cause more regular screen updates. Restart iTerm2 after changing this setting.");
 DEFINE_BOOL(drawOutlineAroundCursor, NO, @"Experimental Features: Draw outline around underline and vertical bar cursors using background color.");
+DEFINE_BOOL(killSessionsOnLogout, NO, @"Experimental Features: Kill sessions on logout.\nA possible fix for issue 4147.");
 @end

sources/iTermController.m

@@ -1448,6 +1448,9 @@ static iTermController *gSharedInstance;
 - (void)workspaceWillPowerOff:(NSNotification *)notification {
     _willPowerOff = YES;
+    if ([iTermAdvancedSettingsModel killSessionsOnLogout] && [iTermAdvancedSettingsModel runJobsInServers]) {
+        [self killRestorableSessions];
+    }
 }
 - (NSInteger)numberOfDecodesPending {