scripts/sstate-cache-management.sh: fix return value by adding exit 0

* usefull for jenkins jobs, which will otherwise fail
  because 1 was returned

(From OE-Core rev: a864de0f2a326f857125229fc986845044931196)

Signed-off-by: Henning Heinold <heinold@inf.fu-berlin.de>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

scripts/sstate-cache-management.sh

@@ -422,4 +422,4 @@ done
 [ -n "$stamps" ] && rm_by_stamps
 [ -z "$rm_duplicated" -a -z "$stamps" ] && \
     echo "What do you want to do?"
-
+exit 0