tdf#101822 Always de-zombie the glxtest process

Make sure we wait for the glxtest process.

Change-Id: I143290b80ba83e35f8d0f95d133c25178c5fe563

vcl/source/opengl/OpenGLHelper.cxx

@@ -1006,14 +1006,11 @@ bool OpenGLHelper::isVCLOpenGLEnabled()
     bForceOpenGL = !!getenv("SAL_FORCEGL") || officecfg::Office::Common::VCL::ForceOpenGL::get();
 
     bool bRet = false;
-    if (bForceOpenGL)
+    // always call supportsVCLOpenGL to de-zombie the glxtest child process on X11
+    if (supportsVCLOpenGL() || bForceOpenGL)
     {
         bRet = true;
     }
-    else if (!supportsVCLOpenGL())
-    {
-        bRet = false;
-    }
     else
     {
         static bool bEnableGLEnv = !!getenv("SAL_ENABLEGL");