Empty sequences (and sequences of empty strings) are normalized
to None, but the member filter code expected a list.
This patch extends a test for missing options to also catch
false values.
The functional change is from `if param_name in options:` to
`if options.get(param_name):`; the rest of the patch is code
de-duplication and tests.
These are CSV params with csv_skipspace set, so on the CLI, empty
set is given as a string with just spaces and commas (including
the empty string).
https://fedorahosted.org/freeipa/ticket/2479
e9d68a7b00