The previous version would trigger sub-pipelines (LTE-2x2, ...) if no MR
had the NSA tag (without a commit, etc). Of course, this would make all
pipelines subsequently fail (as not enough arguments, such as the
commit, were given). In this commit, we read the output of `jq` from
JSON, which will result in an empty list if no MR is tagged with the NSA
label (and the output in the console will be nicer as well).

This reverts commit 29268d0a.

This reverts commit 96554bef

Signed-off-by: Raphael Defosseux <raphael.defosseux@eurecom.fr>

add new nsa reference test

dummy files cleanup