[FIX] tools: find_in_path: config is not ready at import time

commit f76d4525a was not actually working: extra keys from
config files are not yet into the config options dict at
import time. The fix is to move the logic inside the method,
like in `find_pg_tool` just below.

Also fix the use of `find_in_path` in report.py: the subprocess
may also raise AttributeError exception, so instead of listing
all the possible ones just re-raise the IOError shallowed by
`find_in_path` when the result is None.

Fixes #3809 #3811
[FIX] web_kanban: hide kanban_groups when there's no record.

Hide kanban_groups or columns when there's no record to show.
I know this create a problem in time to create a new column, but I think
this is better behaviour for now.