Tolerate whitespace before key in manage_variable_values_ini and set_variable_values_ini

Currently, this can be managed.

[section foo]
key=value

However, if the file looks like this:

[section bar]
  key=value

then the previous regex would not match.

What I can get from the INI spec, is that whitespace is optional. This commit
adds this to the regex, with an optional whitespace match at the beginning of
the line.