patch 8.0.0585: test_options fails when run in the GUI

Problem:    Test_options fails when run in the GUI.
Solution:   Also check the 'imactivatekey' value when the GUI is not running.
            Specify test values that work and that fail.
diff --git a/src/option.c b/src/option.c
index 7e1f5d1..f9d2734 100644
--- a/src/option.c
+++ b/src/option.c
@@ -6403,7 +6403,7 @@
 #if defined(FEAT_XIM) && defined(FEAT_GUI_GTK)
     else if (varp == &p_imak)
     {
-	if (gui.in_use && !im_xim_isvalid_imactivate())
+	if (!im_xim_isvalid_imactivate())
 	    errmsg = e_invarg;
     }
 #endif