libs3: added 'make check' target

Signed-off-by: Sage Weil <sage@inktank.com>

diff --git a/src/libs3 b/src/libs3
index 7165f83c53b05629bc162765808fabc06f1e7306..2f92edd36f73de558957909a0b90af9f755be59c 160000 (submodule)
--- a/src/libs3
+++ b/src/libs3
@@ -1 +1 @@
-Subproject commit 7165f83c53b05629bc162765808fabc06f1e7306
+Subproject commit 2f92edd36f73de558957909a0b90af9f755be59c