CI: Exclude whitespace_test from Valgrind checks
Exclude whitespace_test from Valgrind checks in contrib/ci/run to
prevent it from failing the tests due to Bash bugs.
Reviewed-by: Lukáš Slebodník <lslebodn@redhat.com>
(cherry picked from commit 8dff4a773dd9525ec587cd31646a9f67252122c1)