Ensure terminal cursorBlink is restored after app mode change

Fixes #11049
See also sourcelair/xterm.js#271

src/vs/workbench/parts/terminal/electron-browser/terminalInstance.ts

@@ -299,6 +299,7 @@ export class TerminalInstance implements ITerminalInstance {
 
 	public setCursorBlink(blink: boolean): void {
 		if (this._xterm && this._xterm.cursorBlink !== blink) {
+			this._xterm.options.cursorBlink = blink;
 			this._xterm.cursorBlink = blink;
 			this._xterm.refresh(0, this._xterm.rows - 1);
 		}