tests: valgrind.supp: suppress g_type_register_static leaks

When a type is registered, it holds allocated memory until
the program exits.

Add an exception to valgrind.supp to make the output of
  make -C tests valgrind
more readable.
Signed-off-by: NJán Tomko <jtomko@redhat.com>
Reviewed-by: NMichal Privoznik <mprivozn@redhat.com>

tests/.valgrind.supp

@@ -148,3 +148,16 @@
     fun:virObjectUnref
     fun:main
 }
+#
+# types registered with GLib are never freed
+#
+{
+    glibTypeRegisterLeak
+    Memcheck:Leak
+    match-leak-kinds: possible
+    ...
+    fun:g_realloc
+    obj:*/lib*/libgobject*
+    fun:g_type_register_static
+    ...
+}