Fixed bug in "exiv2 -ix": When writing metadata failed, the exitcode was 0 instead of 1

This issue occured only when reading metadata succeeded,
but writing metadata failed.

src/actions.cpp

@@ -1876,6 +1876,7 @@ namespace {
         catch (const Exiv2::AnyError& e) {
             std::cerr << target <<
                 ": " << _("Could not write metadata to file") << ": " << e << "\n";
+            return 1;
         }
 
         return 0;