builtin/fetch cleanup: always set default value for submodule recursing

builtin/fetch cleanup: always set default value for submodule recursing

The check for the default was introduced with 88a21979c5 (fetch/pull:
recurse into submodules when necessary, 2011-03-06), which replaced an
older construct (builtin/fetchs own implementation of the super-prefix)
introduced in be254a0ea9 (Add the 'fetch.recurseSubmodules' config setting,
2010-11-11) which made sense at the time as there was no default fetch
option for submodules at the time.

Set builtin/fetch.c#recurse_submodules_default to the same value as
submodule.c#config_fetch_recurse_submodules which is set via
set_config_fetch_recurse_submodules, such that the condition for checking
whether we have to set the default value becomes unnecessary.

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