tests: Skip cls-testbed.t if tests/cls dir does not exist

Curently tests/cls-testbed.t tries to run any *.t in
tests/cls/ folder but such folder does not exist.
Signed-off-by: Vadim Kochan <vadim4j@gmail.com>

testsuite/lib/generic.sh

@@ -21,6 +21,11 @@ ts_err_cat()
 	ts_cat "$@" | tee >> $ERRF
 }
 
+ts_skip()
+{
+    exit 127
+}
+
 ts_tc()
 {
 	SCRIPT=$1; shift

testsuite/tests/cls-testbed.t

@@ -5,6 +5,11 @@ source lib/generic.sh
 
 QDISCS="cbq htb dsmark"
 
+if [ ! -d tests/cls ]; then
+    ts_log "tests/cls folder does not exist"
+    ts_skip
+fi
+
 for q in ${QDISCS}; do
 	ts_log "Preparing classifier testbed with qdisc $q"