scripts/config: fix assignment of parameters for short version of --*-after options
When --*-after options are used, two parameters are parsed from the
command-line before the adequate function is called:
- the `before' option, after which the new option will be inserted,
- the name of the option to enable/disable/modularise.
With the short version of --*-after options (namely -E, -D, -M), the
parsing step is not performed which leads to processing unset variables.
Add options -E, -D, -M to the test that triggers assignment of parameters
for --*-after options.