patch 8.0.1245: when WaitFor() has a wrong expression it just waits a second

Problem:    When WaitFor() has a wrong expression it just waits a second,
            which goes unnoticed. (James McCoy)
Solution:   When WaitFor() times out throw an exception.  Fix places where the
            expression was wrong.
diff --git a/src/testdir/test_netbeans.vim b/src/testdir/test_netbeans.vim
index 7bffeb2..4ac03db 100644
--- a/src/testdir/test_netbeans.vim
+++ b/src/testdir/test_netbeans.vim
@@ -27,7 +27,7 @@
 
   " Opening README.txt will result in a setDot command
   call WaitFor('len(readfile("Xnetbeans")) > 4')
-  call WaitFor('getcurpos()[1] == 2')
+  call WaitFor('getcurpos()[1] == 3')
   let pos = getcurpos()
   call assert_equal(3, pos[1])
   call assert_equal(20, pos[2])