Fix globbing of CONFIG_D *.sh files.

Fix globbing of CONFIG_D *.sh files.

With the globbing changes made in
61083cf52231e09e3a9b599d602c06978704ec57 to globally disable globbing by
default, this broke the ability to load the CONFIG_D `*.sh` files.

This re-enables globbing when reading these `*.sh` files and then disables it
again afterwards. Note that this also keeps globbing enabled inside the
loop, when sourcing the individual `*.sh` files for backwards
compatibility (so if the individual config scripts relied on the default
of globbing being enabled, there won't be any change in behavior).