gobject: bindtests: gjs exception behaviour changed, fix test.

When libguestfs calls 'error (g, "error")', gjs in F17 throws
error.message == "Error invoking Guestfs.test0rinterr: error"

In F18, error.message is simply the string "error".

Fix the test so it works for both cases.
(cherry picked from commit 6afb7336e3)

gobject/bindtests-manual.js

@@ -26,7 +26,7 @@ function check_error(f) {
     g[f]();
   } catch (error) {
     threw = true;
-    if (!error.message.match(/: error$/)) {
+    if (!error.message.match(/error$/)) {
       print(f + " threw unexpected error: " + error.message);
       fail = true;
     }