submodule: allow erroneous values for the fetchRecurseSubmodules option

submodule: allow erroneous values for the fetchRecurseSubmodules option

We should not die when reading the submodule config cache since the
user might not be able to get out of that situation when the
configuration is part of the history.

We should handle this condition later when the value is about to be
used.

Signed-off-by: Heiko Voigt <hvoigt@hvoigt.net>
Signed-off-by: Stefan Beller <sbeller@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>