[v9_16] Fix implicit string concatenation in tests-checkds.py
pylint 2.14.2 reports the following warnings:
bin/tests/system/checkds/tests-checkds.py:265:0: W1404: Implicit string concatenation found in call (implicit-str-concat)
bin/tests/system/checkds/tests-checkds.py:273:0: W1404: Implicit string concatenation found in call (implicit-str-concat)
(cherry picked from commit 831ac8ad)