contrib: Fix 2 bugs in check-params-in-docs.py

In my last patch for check-params-in-docs.py I accidentally
1. left one occurence of the 'help_params' variable not renamed
2. converted 'help_params' from a dict to a list

These issues cause the script to error when encountering a parameter
missing in docs.  This patch should fix these issues.

contrib/ChangeLog:

	* check-params-in-docs.py: 'params' -> 'help_params'.  Don't
	convert 'help_params' to a list.

Signed-off-by: Filip Kastl <fkastl@suse.cz>